* [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code interaction
@ 1999-06-19 23:14 Kanoj Sarcar
1999-06-21 13:32 ` Stephen C. Tweedie
0 siblings, 1 reply; 6+ messages in thread
From: Kanoj Sarcar @ 1999-06-19 23:14 UTC (permalink / raw
To: linux-mm; +Cc: torvalds, sct, andrea
There is no reason for shared memory pages to have to be marked
PG_swap_cache to fool the underlying swap io routines. Not doing
this will also make sure shrink_mmap does not steal such pages,
and an extra page reference bumping is not neccesary to ensure
this. Also, this makes things more consistent, in the sense
that pages marked PG_swap_cache are always in the swap cache,
and vice versa.
Kanoj
kanoj@engr.sgi.com
--- /usr/tmp/p_rdiff_a005Qw/page_io.c Sat Jun 19 16:03:22 1999
+++ mm/page_io.c Sat Jun 19 15:01:45 1999
@@ -35,7 +35,7 @@
* that shared pages stay shared while being swapped.
*/
-static void rw_swap_page_base(int rw, unsigned long entry, struct page *page, int wait)
+static void rw_swap_page_base(int rw, unsigned long entry, struct page *page, int wait, int shmfs)
{
unsigned long type, offset;
struct swap_info_struct * p;
@@ -84,7 +84,7 @@
return;
}
- if (PageSwapCache(page)) {
+ if (!shmfs) {
/* Make sure we are the only process doing I/O with this swap page. */
while (test_and_set_bit(offset,p->swap_lockmap)) {
run_task_queue(&tq_disk);
@@ -162,7 +162,7 @@
/* Do some cleaning up so if this ever happens we can hopefully
* trigger controlled shutdown.
*/
- if (PageSwapCache(page)) {
+ if (!shmfs) {
if (!test_and_clear_bit(offset,p->swap_lockmap))
printk("swap_after_unlock_page: lock already cleared\n");
wake_up(&lock_queue);
@@ -174,7 +174,7 @@
set_bit(PG_decr_after, &page->flags);
atomic_inc(&nr_async_pages);
}
- if (PageSwapCache(page)) {
+ if (!shmfs) {
/* only lock/unlock swap cache pages! */
set_bit(PG_swap_unlock_after, &page->flags);
}
@@ -256,7 +256,7 @@
printk ("swap entry mismatch");
return;
}
- rw_swap_page_base(rw, entry, page, wait);
+ rw_swap_page_base(rw, entry, page, wait, 0);
}
/*
@@ -270,7 +270,7 @@
page = mem_map + MAP_NR((unsigned long) buffer);
wait_on_page(page);
set_bit(PG_locked, &page->flags);
- if (test_and_set_bit(PG_swap_cache, &page->flags)) {
+ if (test_bit(PG_swap_cache, &page->flags)) {
printk ("VM: read_swap_page: page already in swap cache!\n");
return;
}
@@ -278,13 +278,9 @@
printk ("VM: read_swap_page: page already in page cache!\n");
return;
}
- page->inode = &swapper_inode;
page->offset = entry;
- atomic_inc(&page->count); /* Protect from shrink_mmap() */
- rw_swap_page(rw, entry, buffer, 1);
+ rw_swap_page_base(rw, entry, page, 1, 0);
atomic_dec(&page->count);
- page->inode = 0;
- clear_bit(PG_swap_cache, &page->flags);
}
/*
@@ -305,5 +301,5 @@
printk ("VM: rw_swap_page_nolock: page in swap cache!\n");
return;
}
- rw_swap_page_base(rw, entry, page, wait);
+ rw_swap_page_base(rw, entry, page, wait, 1);
}
--- /usr/tmp/p_rdiff_a005UY/swap.h Sat Jun 19 16:05:33 1999
+++ include/linux/swap.h Sat Jun 19 15:05:43 1999
@@ -144,13 +144,6 @@
extern unsigned long swap_cache_find_success;
#endif
-extern inline unsigned long in_swap_cache(struct page *page)
-{
- if (PageSwapCache(page))
- return page->offset;
- return 0;
-}
-
/*
* Work out if there are any other processes sharing this page, ignoring
* any page reference coming from the swap cache, or from outstanding
--
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code interaction
1999-06-19 23:14 [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code interaction Kanoj Sarcar
@ 1999-06-21 13:32 ` Stephen C. Tweedie
1999-06-21 17:17 ` Kanoj Sarcar
0 siblings, 1 reply; 6+ messages in thread
From: Stephen C. Tweedie @ 1999-06-21 13:32 UTC (permalink / raw
To: Kanoj Sarcar; +Cc: linux-mm, torvalds, sct, andrea
Hi,
On Sat, 19 Jun 1999 16:14:26 -0700 (PDT), kanoj@google.engr.sgi.com
(Kanoj Sarcar) said:
> There is no reason for shared memory pages to have to be marked
> PG_swap_cache to fool the underlying swap io routines.
That code was never intended to "fool" anyone: the swap IO code is able
to do read/write swap even in the absense of swap cache entries for the
page. Only recently have we forced all swap to go through the swap
cache, but the IO routines are still capable of doing it both ways.
> - if (PageSwapCache(page)) {
> + if (!shmfs) {
> /* Make sure we are the only process doing I/O with this swap page. */
> while (test_and_set_bit(offset,p->swap_lockmap)) {
> run_task_queue(&tq_disk);
This looks wrong, conceptually. I'd prefer to see us do the locking any
time the page happens to have an appropriate swap lock map bit.
PageSwapCache() is the right test in this case: the rw_swap_page stuff
shouldn't care about whether it is shmfs calling it or not. It should
just care about doing the swap cache locking correctly if that happens
to be required.
--Stephen
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code interaction
1999-06-21 13:32 ` Stephen C. Tweedie
@ 1999-06-21 17:17 ` Kanoj Sarcar
1999-06-21 17:51 ` Stephen C. Tweedie
0 siblings, 1 reply; 6+ messages in thread
From: Kanoj Sarcar @ 1999-06-21 17:17 UTC (permalink / raw
To: Stephen C. Tweedie; +Cc: linux-mm, torvalds, andrea
>
> Hi,
>
> On Sat, 19 Jun 1999 16:14:26 -0700 (PDT), kanoj@google.engr.sgi.com
> (Kanoj Sarcar) said:
>
> > There is no reason for shared memory pages to have to be marked
> > PG_swap_cache to fool the underlying swap io routines.
>
> That code was never intended to "fool" anyone: the swap IO code is able
> to do read/write swap even in the absense of swap cache entries for the
> page. Only recently have we forced all swap to go through the swap
> cache, but the IO routines are still capable of doing it both ways.
>
> > - if (PageSwapCache(page)) {
> > + if (!shmfs) {
> > /* Make sure we are the only process doing I/O with this swap page. */
> > while (test_and_set_bit(offset,p->swap_lockmap)) {
> > run_task_queue(&tq_disk);
>
> This looks wrong, conceptually. I'd prefer to see us do the locking any
> time the page happens to have an appropriate swap lock map bit.
> PageSwapCache() is the right test in this case: the rw_swap_page stuff
> shouldn't care about whether it is shmfs calling it or not. It should
> just care about doing the swap cache locking correctly if that happens
> to be required.
>
> --Stephen
>
Okay, wrong choice of name on the parameter "shmfs". Would it help
to think of the new last parameter to rw_swap_page_base as "dolock",
which the caller has to pass in to indicate whether there is a
swap lock map bit?
I am reposting the patch with this change, specially since there
is a page reference count problem on the original patch.
Thanks.
Kanoj
kanoj@engr.sgi.com
--- mm/page_io.old Mon Jun 7 13:49:17 1999
+++ mm/page_io.c Mon Jun 21 09:09:33 1999
@@ -35,7 +35,7 @@
* that shared pages stay shared while being swapped.
*/
-static void rw_swap_page_base(int rw, unsigned long entry, struct page *page, int wait)
+static void rw_swap_page_base(int rw, unsigned long entry, struct page *page, int wait, int dolock)
{
unsigned long type, offset;
struct swap_info_struct * p;
@@ -84,7 +84,7 @@
return;
}
- if (PageSwapCache(page)) {
+ if (dolock) {
/* Make sure we are the only process doing I/O with this swap page. */
while (test_and_set_bit(offset,p->swap_lockmap)) {
run_task_queue(&tq_disk);
@@ -162,7 +162,7 @@
/* Do some cleaning up so if this ever happens we can hopefully
* trigger controlled shutdown.
*/
- if (PageSwapCache(page)) {
+ if (dolock) {
if (!test_and_clear_bit(offset,p->swap_lockmap))
printk("swap_after_unlock_page: lock already cleared\n");
wake_up(&lock_queue);
@@ -174,7 +174,7 @@
set_bit(PG_decr_after, &page->flags);
atomic_inc(&nr_async_pages);
}
- if (PageSwapCache(page)) {
+ if (dolock) {
/* only lock/unlock swap cache pages! */
set_bit(PG_swap_unlock_after, &page->flags);
}
@@ -256,7 +256,7 @@
printk ("swap entry mismatch");
return;
}
- rw_swap_page_base(rw, entry, page, wait);
+ rw_swap_page_base(rw, entry, page, wait, 1);
}
/*
@@ -270,7 +270,7 @@
page = mem_map + MAP_NR((unsigned long) buffer);
wait_on_page(page);
set_bit(PG_locked, &page->flags);
- if (test_and_set_bit(PG_swap_cache, &page->flags)) {
+ if (test_bit(PG_swap_cache, &page->flags)) {
printk ("VM: read_swap_page: page already in swap cache!\n");
return;
}
@@ -278,13 +278,8 @@
printk ("VM: read_swap_page: page already in page cache!\n");
return;
}
- page->inode = &swapper_inode;
page->offset = entry;
- atomic_inc(&page->count); /* Protect from shrink_mmap() */
- rw_swap_page(rw, entry, buffer, 1);
- atomic_dec(&page->count);
- page->inode = 0;
- clear_bit(PG_swap_cache, &page->flags);
+ rw_swap_page_base(rw, entry, page, 1, 1);
}
/*
@@ -305,5 +300,5 @@
printk ("VM: rw_swap_page_nolock: page in swap cache!\n");
return;
}
- rw_swap_page_base(rw, entry, page, wait);
+ rw_swap_page_base(rw, entry, page, wait, 0);
}
--- /usr/tmp/p_rdiff_a005UY/swap.h Sat Jun 19 16:05:33 1999
+++ include/linux/swap.h Sat Jun 19 15:05:43 1999
@@ -144,13 +144,6 @@
extern unsigned long swap_cache_find_success;
#endif
-extern inline unsigned long in_swap_cache(struct page *page)
-{
- if (PageSwapCache(page))
- return page->offset;
- return 0;
-}
-
/*
* Work out if there are any other processes sharing this page, ignoring
* any page reference coming from the swap cache, or from outstanding
--
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code interaction
1999-06-21 17:17 ` Kanoj Sarcar
@ 1999-06-21 17:51 ` Stephen C. Tweedie
1999-06-21 18:31 ` Andrea Arcangeli
0 siblings, 1 reply; 6+ messages in thread
From: Stephen C. Tweedie @ 1999-06-21 17:51 UTC (permalink / raw
To: Kanoj Sarcar; +Cc: Stephen C. Tweedie, linux-mm, torvalds, andrea
Hi,
On Mon, 21 Jun 1999 10:17:10 -0700 (PDT), kanoj@google.engr.sgi.com
(Kanoj Sarcar) said:
> Okay, wrong choice of name on the parameter "shmfs". Would it help
> to think of the new last parameter to rw_swap_page_base as "dolock",
> which the caller has to pass in to indicate whether there is a
> swap lock map bit?
Maybe, but I still don't see what it buys.
--Stephen
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code interaction
1999-06-21 17:51 ` Stephen C. Tweedie
@ 1999-06-21 18:31 ` Andrea Arcangeli
1999-06-21 19:12 ` [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code Kanoj Sarcar
0 siblings, 1 reply; 6+ messages in thread
From: Andrea Arcangeli @ 1999-06-21 18:31 UTC (permalink / raw
To: Stephen C. Tweedie; +Cc: Kanoj Sarcar, linux-mm, torvalds
On Mon, 21 Jun 1999, Stephen C. Tweedie wrote:
>On Mon, 21 Jun 1999 10:17:10 -0700 (PDT), kanoj@google.engr.sgi.com
>(Kanoj Sarcar) said:
>
>> Okay, wrong choice of name on the parameter "shmfs". Would it help
>> to think of the new last parameter to rw_swap_page_base as "dolock",
>> which the caller has to pass in to indicate whether there is a
>> swap lock map bit?
Kanoj did you took a look at my VM (I pointed out to you the url some time
ago). Here I just safely removed the swaplockmap completly. All the
page-contentions get automagically resolved from the swap cache also for
shm.c. I sent the relevant patches to Linus just before the page cache
code gone and the new page/buffer cache broken them in part. But now I am
running again rock solid with 2.3.7_andrea1 with SMP so if Linus will
agree I'll return to send him patches about such shm/swap-lockmap issue.
Just to show you:
andrea@laser:/usr/src$ cvs diff -u -r linux-2_3_7 linux/mm/page_io.c|diffstat
page_io.c | 129 ++------------------------------------------------------------
1 files changed, 6 insertions, 123 deletions
(should be enough to explain the thing :)
Andrea Arcangeli
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code
1999-06-21 18:31 ` Andrea Arcangeli
@ 1999-06-21 19:12 ` Kanoj Sarcar
0 siblings, 0 replies; 6+ messages in thread
From: Kanoj Sarcar @ 1999-06-21 19:12 UTC (permalink / raw
To: Andrea Arcangeli; +Cc: sct, linux-mm, torvalds
>
> On Mon, 21 Jun 1999, Stephen C. Tweedie wrote:
>
> >On Mon, 21 Jun 1999 10:17:10 -0700 (PDT), kanoj@google.engr.sgi.com
> >(Kanoj Sarcar) said:
> >
> >> Okay, wrong choice of name on the parameter "shmfs". Would it help
> >> to think of the new last parameter to rw_swap_page_base as "dolock",
> >> which the caller has to pass in to indicate whether there is a
> >> swap lock map bit?
>
> Kanoj did you took a look at my VM (I pointed out to you the url some time
> ago). Here I just safely removed the swaplockmap completly. All the
> page-contentions get automagically resolved from the swap cache also for
> shm.c. I sent the relevant patches to Linus just before the page cache
> code gone and the new page/buffer cache broken them in part. But now I am
> running again rock solid with 2.3.7_andrea1 with SMP so if Linus will
> agree I'll return to send him patches about such shm/swap-lockmap issue.
> Just to show you:
>
I skimmed thru your patch earlier, but was too lazy to concentrate
on the details ...
I took the time now to look into your changes to page_io.c and shm.c,
and I like it better than the current code, for the reason that pages
marked PageSwapCache will actually end up being in the swap cache.
Which is what I was trying to do in my patch ...
If Linus is willing to take your patch, we can stop talking about
mine ...
Thanks.
Kanoj
kanoj@engr.sgi.com
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~1999-06-21 19:12 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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1999-06-19 23:14 [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code interaction Kanoj Sarcar
1999-06-21 13:32 ` Stephen C. Tweedie
1999-06-21 17:17 ` Kanoj Sarcar
1999-06-21 17:51 ` Stephen C. Tweedie
1999-06-21 18:31 ` Andrea Arcangeli
1999-06-21 19:12 ` [RFC] [RFT] [PATCH] kanoj-mm9-2.2.10 simplify swapcache/shm code Kanoj Sarcar
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