From: Chuck Lever <cel@monkey.org>
To: "Benjamin C.R. LaHaise" <blah@kvack.org>
Cc: Linus Torvalds <torvalds@transmeta.com>, linux-mm@kvack.org
Subject: Re: [patch] mmap<->write deadlock fix, plus bug in block_write_zero_range
Date: Wed, 22 Dec 1999 23:00:40 -0500 (EST) [thread overview]
Message-ID: <Pine.BSO.4.10.9912222254540.25860-100000@funky.monkey.org> (raw)
In-Reply-To: <Pine.LNX.3.96.991222103000.22064A-100000@kanga.kvack.org>
On Wed, 22 Dec 1999, Benjamin C.R. LaHaise wrote:
> On Wed, 22 Dec 1999, Chuck Lever wrote:
> > On Wed, 22 Dec 1999, Benjamin C.R. LaHaise wrote:
> > i've tried this before several times. i could never get the system to
> > perform as well under benchmark load using find_page_nolock as when using
> > find_get_page. the throughput difference was about 5%, if i recall. i
> > haven't explained this to myself yet.
>
> Here's my hypothesis about why find_page_nolock vs find_get_page makes a
> difference: using find_page_nolock means that we'll never do a
> run_task_queue(&tq_disk); to get our async readahead requests run. So, in
> theory, doing that in filemap_nopage will restore performance. Isn't
> there a way that the choice of when to run tq_disk could be made a bit
> less arbitrary?
this patch appears to have negligible effect on benchmark throughput
measurements, whereas, without the run_task_queue, throughput drops.
btw, i notice that a "read_cache_page" function has appeared that looks
similar to "page_cache_read" -- is there necessity for both?
--- linux-2.3.34-ref/mm/filemap.c Wed Dec 22 21:23:03 1999
+++ linux/mm/filemap.c Wed Dec 22 22:53:19 1999
@@ -1325,9 +1325,13 @@
*/
hash = page_hash(&inode->i_data, pgoff);
retry_find:
- page = __find_get_page(&inode->i_data, pgoff, hash);
+ spin_lock(&pagecache_lock);
+ page = __find_page_nolock(&inode->i_data, pgoff, *hash);
if (!page)
goto no_cached_page;
+ get_page(page);
+ spin_unlock(&pagecache_lock);
+ run_task_queue(&tq_disk);
/*
* Ok, found a page in the page cache, now we need to check
@@ -1358,6 +1362,8 @@
return old_page;
no_cached_page:
+ spin_unlock(&pagecache_lock);
+
/*
* If the requested offset is within our file, try to read a whole
* cluster of pages at once.
- Chuck Lever
--
corporate: <chuckl@netscape.com>
personal: <chucklever@netscape.net> or <cel@monkey.org>
The Linux Scalability project:
http://www.citi.umich.edu/projects/linux-scalability/
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prev parent reply other threads:[~1999-12-23 4:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-12-22 5:58 [patch] mmap<->write deadlock fix, plus bug in block_write_zero_range Benjamin C.R. LaHaise
1999-12-22 15:08 ` Chuck Lever
1999-12-22 15:43 ` Benjamin C.R. LaHaise
1999-12-22 15:58 ` Chuck Lever
1999-12-23 4:00 ` Chuck Lever [this message]
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