From: Matthew Wilcox <willy@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
William Kucharski <william.kucharski@oracle.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Yang Shi <yang.shi@linux.alibaba.com>,
Dave Chinner <dchinner@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 12/12] mm/filemap: Return only head pages from find_get_entries
Date: Sun, 25 Oct 2020 23:19:34 +0000 [thread overview]
Message-ID: <20201025231934.GL20115@casper.infradead.org> (raw)
In-Reply-To: <20201001071728.GA17860@quack2.suse.cz>
On Thu, Oct 01, 2020 at 09:17:28AM +0200, Jan Kara wrote:
> > I have a followup patch which isn't part of this series which fixes it:
> >
> > http://git.infradead.org/users/willy/pagecache.git/commitdiff/364283163847d1c106463223b858308c730592a1
>
> Yeah, that looks good. How about partial THPs? The way you've implemented
> it we will now possibly evict more than strictly required. But OTOH
> evicting exactly may require THP split which is a bit unfortunate. But
> probably still a better option because otherwise we could have pages being
> repeatedly brought in and out of cache just because e.g. workload mixes
> direct and buffered IO and is not aligned to THP boundary (and although I
> find loads mixing buffered and direct IO to the same file badly designed,
> I know for a fact that they do exist and if the file ranges are not
> overlapping, it is not that insane design).
Sorry, forgot to reply to this.
In this patchset, THPs are created by readahead. We always start
out by allocating order-0 pages and only ramp up after hitting a page
marked as PageReadahead. So it's not like tmpfs where we'll try to jump
straight to order-9 pages and have to worry about the behaviour you're
describing above. That means in this kind of scenario, we might have,
eg, an order-6 page in the cache, remove the whole thing, then bring
back in some order-0 pages. If we hit on those, we'll bring in some
order-2 pages. We won't bring in order-6 pages again until we've hit
in the readahead window twice more.
I think the ramp-up is probably too aggressive, but it's fun for testing.
next prev parent reply other threads:[~2020-10-25 23:19 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-14 13:00 [PATCH v2 00/12] Overhaul multi-page lookups for THP Matthew Wilcox (Oracle)
2020-09-14 13:00 ` [PATCH v2 01/12] mm: Make pagecache tagged lookups return only head pages Matthew Wilcox (Oracle)
2020-09-29 9:13 ` Jan Kara
2020-09-14 13:00 ` [PATCH v2 02/12] mm/shmem: Use pagevec_lookup in shmem_unlock_mapping Matthew Wilcox (Oracle)
2020-09-29 8:28 ` Jan Kara
2020-09-29 18:36 ` Matthew Wilcox
2020-09-14 13:00 ` [PATCH v2 03/12] mm/filemap: Add helper for finding pages Matthew Wilcox (Oracle)
2020-09-29 8:27 ` Jan Kara
2020-09-14 13:00 ` [PATCH v2 04/12] mm/filemap: Add mapping_seek_hole_data Matthew Wilcox (Oracle)
2020-09-29 8:46 ` Jan Kara
2020-09-29 12:42 ` Matthew Wilcox
2020-09-29 13:39 ` Matthew Wilcox
2020-09-14 13:00 ` [PATCH v2 05/12] mm: Add and use find_lock_entries Matthew Wilcox (Oracle)
2020-09-29 8:58 ` Jan Kara
2020-09-29 12:48 ` Matthew Wilcox
2020-09-30 10:40 ` Jan Kara
2020-09-14 13:00 ` [PATCH v2 06/12] mm: Add an 'end' parameter to find_get_entries Matthew Wilcox (Oracle)
2020-09-14 13:00 ` [PATCH v2 07/12] mm: Add an 'end' parameter to pagevec_lookup_entries Matthew Wilcox (Oracle)
2020-09-29 9:02 ` Jan Kara
2020-09-14 13:00 ` [PATCH v2 08/12] mm: Remove nr_entries parameter from pagevec_lookup_entries Matthew Wilcox (Oracle)
2020-09-29 9:03 ` Jan Kara
2020-09-14 13:00 ` [PATCH v2 09/12] mm: Pass pvec directly to find_get_entries Matthew Wilcox (Oracle)
2020-09-29 9:07 ` Jan Kara
2020-09-14 13:00 ` [PATCH v2 10/12] mm: Remove pagevec_lookup_entries Matthew Wilcox (Oracle)
2020-09-29 9:08 ` Jan Kara
2020-09-14 13:00 ` [PATCH v2 11/12] mm/truncate,shmem: Handle truncates that split THPs Matthew Wilcox (Oracle)
2020-09-30 11:59 ` Jan Kara
2020-09-30 14:51 ` Matthew Wilcox
2020-09-14 13:00 ` [PATCH v2 12/12] mm/filemap: Return only head pages from find_get_entries Matthew Wilcox (Oracle)
2020-09-30 12:15 ` Jan Kara
2020-09-30 12:36 ` Matthew Wilcox
2020-09-30 17:08 ` Jan Kara
2020-09-30 17:23 ` Matthew Wilcox
2020-10-01 7:17 ` Jan Kara
2020-10-25 23:19 ` Matthew Wilcox [this message]
2020-10-26 9:11 ` Jan Kara
2020-09-28 20:13 ` [PATCH v2 00/12] Overhaul multi-page lookups for THP Matthew Wilcox
2020-09-29 8:50 ` William Kucharski
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=20201025231934.GL20115@casper.infradead.org \
--to=willy@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=dchinner@redhat.com \
--cc=hannes@cmpxchg.org \
--cc=hughd@google.com \
--cc=jack@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=william.kucharski@oracle.com \
--cc=yang.shi@linux.alibaba.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