From: Andrew Morton <akpm@linux-foundation.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>, linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Sahkeel Butt <shakeelb@google.com>,
Minchan Kim <minchan@google.com>
Subject: Re: [PATCH] mm: annotate refault stalls from swap_readpage
Date: Fri, 11 Oct 2019 14:32:31 -0700 [thread overview]
Message-ID: <20191011143231.e338e0ef337492e83233ad39@linux-foundation.org> (raw)
In-Reply-To: <20191010191747.GA31673@cmpxchg.org>
On Thu, 10 Oct 2019 15:17:47 -0400 Johannes Weiner <hannes@cmpxchg.org> wrote:
> On Thu, Oct 10, 2019 at 08:21:34AM -0700, Minchan Kim wrote:
> > From: Minchan Kim <minchan@google.com>
> >
> > If block device supports rw_page operation, it doesn't submit bio
> > so annotation in submit_bio for refault stall doesn't work.
> > It happens with zram in android, especially swap read path which
> > could consume CPU cycle for decompress. It is also a problem for
> > zswap which uses frontswap.
> >
> > Annotate swap_readpage() to account the synchronous IO overhead
> > to prevent underreport memory pressure.
> >
> > Cc: Johannes Weiner <hannes@cmpxchg.org>
> > Signed-off-by: Minchan Kim <minchan@google.com>
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
>
> Can you please add a comment to the caller? Lifted from submit_bio():
>
> /*
> * Count submission time as memory stall. When the device is
> * congested, or the submitting cgroup IO-throttled,
> * submission can be a significant part of overall IO time.
> */
This?
--- a/mm/page_io.c~mm-annotate-refault-stalls-from-swap_readpage-fix
+++ a/mm/page_io.c
@@ -361,6 +361,11 @@ int swap_readpage(struct page *page, boo
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageUptodate(page), page);
+ /*
+ * Count submission time as memory stall. When the device is congested,
+ * or the submitting cgroup IO-throttled, submission can be a
+ * significant part of overall IO time.
+ */
psi_memstall_enter(&pflags);
if (frontswap_load(page) == 0) {
_
prev parent reply other threads:[~2019-10-11 21:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-10 15:21 [PATCH] mm: annotate refault stalls from swap_readpage Minchan Kim
2019-10-10 19:17 ` Johannes Weiner
2019-10-10 22:11 ` Minchan Kim
2019-10-11 17:32 ` Shakeel Butt
2019-10-11 21:32 ` Andrew Morton [this message]
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