From: David Hildenbrand <david@redhat.com>
To: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
hyesoo.yu@samsung.com, mhocko@suse.com, surenb@google.com,
pullip.cho@samsung.com, joaodias@google.com, hridya@google.com,
john.stultz@linaro.org, sumit.semwal@linaro.org,
linux-media@vger.kernel.org, devicetree@vger.kernel.org,
hch@infradead.org, robh+dt@kernel.org,
linaro-mm-sig@lists.linaro.org
Subject: Re: [PATCH v3 2/4] mm: failfast mode with __GFP_NORETRY in alloc_contig_range
Date: Wed, 13 Jan 2021 09:39:26 +0100 [thread overview]
Message-ID: <723e935f-3aa4-2c55-8d69-fcaf71f4eb4c@redhat.com> (raw)
In-Reply-To: <20210113012143.1201105-3-minchan@kernel.org>
On 13.01.21 02:21, Minchan Kim wrote:
> Contiguous memory allocation can be stalled due to waiting
> on page writeback and/or page lock which causes unpredictable
> delay. It's a unavoidable cost for the requestor to get *big*
> contiguous memory but it's expensive for *small* contiguous
> memory(e.g., order-4) because caller could retry the request
> in diffrent range where would have easy migratable pages
> without stalling.
s/diffrent/different/
>
> This patch introduce __GFP_NORETRY as compaction gfp_mask in
> alloc_contig_range so it will fail fast without blocking
> when it encounters pages needed waitting.
s/waitting/waiting/
>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> mm/page_alloc.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5b3923db9158..ff41ceb4db51 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8489,12 +8489,16 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
> unsigned int nr_reclaimed;
> unsigned long pfn = start;
> unsigned int tries = 0;
> + unsigned int max_tries = 5;
> int ret = 0;
> struct migration_target_control mtc = {
> .nid = zone_to_nid(cc->zone),
> .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
> };
>
> + if (cc->alloc_contig && cc->mode == MIGRATE_ASYNC)
> + max_tries = 1;
> +
> migrate_prep();
>
> while (pfn < end || !list_empty(&cc->migratepages)) {
> @@ -8511,7 +8515,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
> break;
> }
> tries = 0;
> - } else if (++tries == 5) {
> + } else if (++tries == max_tries) {
> ret = ret < 0 ? ret : -EBUSY;
> break;
> }
> @@ -8562,7 +8566,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> .nr_migratepages = 0,
> .order = -1,
> .zone = page_zone(pfn_to_page(start)),
> - .mode = MIGRATE_SYNC,
> + .mode = gfp_mask & __GFP_NORETRY ? MIGRATE_ASYNC : MIGRATE_SYNC,
> .ignore_skip_hint = true,
> .no_set_skip_hint = true,
> .gfp_mask = current_gfp_context(gfp_mask),
>
I'm fine with using gfp flags (e.g., __GFP_NORETRY) as long as they
don't enable other implicit behavior (e.g., move draining X to the
caller) that's hard to get from the flag name.
IMHO, if we ever want to move draining to the caller, or change the
behavior of alloc_contig_range() in different ways (e.g., disable PCP),
we won't get around introducing a separate set of flags for
alloc_contig_range().
Let's see what Michal thinks. Thanks!
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-01-13 8:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 1:21 [PATCH v3 0/4] Chunk Heap Support on DMA-HEAP Minchan Kim
2021-01-13 1:21 ` [PATCH v3 1/4] mm: cma: introduce gfp flag in cma_alloc instead of no_warn Minchan Kim
2021-01-20 21:08 ` Suren Baghdasaryan
2021-01-13 1:21 ` [PATCH v3 2/4] mm: failfast mode with __GFP_NORETRY in alloc_contig_range Minchan Kim
2021-01-13 8:39 ` David Hildenbrand [this message]
2021-01-14 18:04 ` Minchan Kim
2021-01-13 1:21 ` [PATCH v3 3/4] dt-bindings: reserved-memory: Make DMA-BUF CMA heap DT-configurable Minchan Kim
2021-01-13 15:45 ` Rob Herring
2021-01-13 17:30 ` Hridya Valsaraju
2021-01-14 14:01 ` Rob Herring
2021-01-14 19:49 ` Hridya Valsaraju
2021-01-13 1:21 ` [PATCH v3 4/4] dma-buf: heaps: add chunk heap to dmabuf heaps Minchan Kim
2021-01-13 3:11 ` kernel test robot
2021-01-14 1:04 ` Minchan Kim
2021-01-13 3:38 ` Randy Dunlap
2021-01-14 1:04 ` Minchan Kim
2021-01-13 6:25 ` kernel test robot
2021-01-19 15:51 ` Minchan Kim
2021-01-19 18:29 ` John Stultz
2021-01-19 20:36 ` Minchan Kim
2021-01-20 3:32 ` Hyesoo Yu
2021-01-20 20:53 ` Suren Baghdasaryan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=723e935f-3aa4-2c55-8d69-fcaf71f4eb4c@redhat.com \
--to=david@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=devicetree@vger.kernel.org \
--cc=hch@infradead.org \
--cc=hridya@google.com \
--cc=hyesoo.yu@samsung.com \
--cc=joaodias@google.com \
--cc=john.stultz@linaro.org \
--cc=linaro-mm-sig@lists.linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=minchan@kernel.org \
--cc=pullip.cho@samsung.com \
--cc=robh+dt@kernel.org \
--cc=sumit.semwal@linaro.org \
--cc=surenb@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).