From: Suraj Choudhari <surajschoudhari@gmail.com>
To: linux-newbie@vger.kernel.org
Subject: Query - Related to kernel changes for GFP_NOIO flag
Date: Sun, 5 Mar 2017 14:37:17 +0530 [thread overview]
Message-ID: <CAGvB2rP=C6AdDw=43pRhS85wbrxcpXE6cypXc=hSdQfJx=q-Fg@mail.gmail.com> (raw)
Hi,
The GFP_NOIO flag used for kmalloc is currently defined to be '__GFP_RECLAIM'
#define GFP_NOIO (__GFP_RECLAIM)
#define __GFP_RECLAIM ((__force
gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM
However, prior to 4.4 kernel, this flag was defined as __GFP_WAIT.
#define GFP_NOIO (__GFP_WAIT)
Queries -
======
1] Can any physical disk IO happen due to memory allocation done
using 'GFP_NOIO' ?
The reason to ask is since the GFP_NOIO is now modified to use
__GFP_KSWAPD_RECLAIM, so I am thinking that physical disk IO may
probably happen whiel swapping the stale pages to disk in kswapd.
2] If kernel code wants to use kmalloc() and wants to ensure there is
NO any physical/disk IO due to kmalloc, shall the kernel code use
__GFP_DIRECT_RECLAIM instead of GFP_NOIO ?
Thanks,
Suraj
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reply other threads:[~2017-03-05 9:07 UTC|newest]
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