Re: [PATCH] vmscan: set try_to_release_page's gfp_mask to 0

Andrew Morton
2008-10-16T02:54:58Z

On Thu, 16 Oct 2008 11:44:39 +0900 Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp> wrote:

> Hi Andrew.
>
> >Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp> wrote:
> >
> >> At 12:21 08/08/13, Andrew Morton wrote:
> >> >On Wed, 13 Aug 2008 11:21:16 +0900 Hisashi Hifumi
> >> ><hifumi.hisashi@oss.ntt.co.jp> wrote:
>
> >> >> Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
> >> >>
> >> >> diff -Nrup linux-2.6.27-rc2.org/mm/vmscan.c
> >linux-2.6.27-rc2.vmscan/mm/vmscan.c
> >> >> --- linux-2.6.27-rc2.org/mm/vmscan.c 2008-08-11 14:33:24.000000000 +0900
> >> >> +++ linux-2.6.27-rc2.vmscan/mm/vmscan.c 2008-08-12 18:57:05.000000000 +0900
> >> >> @@ -614,7 +614,7 @@ static unsigned long shrink_page_list(st
> >> >> * Otherwise, leave the page on the LRU so it is swappable.
> >> >> */
> >> >> if (PagePrivate(page)) {
> >> >> - if (!try_to_release_page(page, sc->gfp_mask))
> >> >> + if (!try_to_release_page(page, 0))
> >> >> goto activate_locked;
> >> >> if (!mapping && page_count(page) == 1) {
> >> >> unlock_page(page);
> >> >
> >> >I think the change makes sense.
> >> >
> >> >Has this change been shown to improve any workloads? If so, please
> >> >provide full information for the changelog. If not, please mention
> >> >this and explain why benefits were not demonstrable. This information
> >> >should _always_ be present in a "performance" patch's changelog!
> >>
> >> Sorry, I do not have performance number yet. I'll try this.
> >>
> >
>
> Unfortunately, I did not succeed to get good performance number that
> prove this patch had some benefit.

OK, thanks, I dropped it.

> >This patch remains in a stalled state...
> >
> >And then there's this:
> >
>
> >:
> >: Really, I think what this patch tells us is that 3f31fddf ("jbd: fix
> >: race between free buffer and commit transaction") was an unpleasant
> >: hack which had undesirable and unexpected side-effects. I think - that
> >: depends upon your as-yet-undisclosed testing results?
> >:
> >: Perhaps we should revert 3f31fddf and have another think about how to
> >: fix the direct-io -EIO problem. One option would be to hold our noses
> >: and add a new gfp_t flag for this specific purpose?
> >:
>
> direct-io -EIO problem was already fixed by following patch.
>
> commit 6ccfa806a9cfbbf1cd43d5b6aa47ef2c0eb518fd
> Author: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
> Date: Tue Sep 2 14:35:40 2008 -0700
>
> VFS: fix dio write returning EIO when try_to_release_page fails
>
> Dio falls back to buffered write when dio write gets EIO due to failure of try_to_release_page
> by above patch. So I think just reverting the patch 3f31fddf ("jbd: fix race between
> free buffer and commit transaction") is good approach.

Fair enough. Could I ask that you (or someone) send a suitable patch
sometime?

I could generate the patch, but I'd never get around to testing it.
Too busy fixing rejects and compile errors :(