From: Chris Webb <chris@arachsys.com>
To: Kent Overstreet <kent.overstreet@gmail.com>
Cc: linux-bcachefs@vger.kernel.org
Subject: Re: More eager discard behaviour
Date: Sat, 6 Nov 2021 21:36:50 +0000 [thread overview]
Message-ID: <20211106213649.GN11670@arachsys.com> (raw)
In-Reply-To: <YYbZii7HNJ8lb8FF@moria.home.lan>
Kent Overstreet <kent.overstreet@gmail.com> writes:
> On Sat, Nov 06, 2021 at 05:11:56PM +0000, Chris Webb wrote:
> > How practical would it be either to more-greedily wake the allocator thread
> > and reclaim buckets, or to detect buckets available to discard earlier in
> > their lifetime?
>
> It's on the todo list, it'll be part of the grand allocator rework I have
> planned - there's a lot that needs to be done.
I read your discussion on the status update and in the related write-up on
the accounting code. It makes a lot of sense to me, given the tried and
tested btree layer is there to be used.
> We've got to rework the state transitions, and differentiate between buckets
> with cached data, buckets that need a journal commit before we can write to them
> again, buckets that need discarding, and buckets that are ready for use - and we
> need to start storing all that persistently, as well as build some new data
> structures to get rid of the scanning over every bucket we currently have to do
> in various places.
>
> Step one is going to be creating a persistent LRU. It'll be another btree,
> sorted by the order in which we want to reuse buckets - a combination of the
> amount of live data in the bucket and the time since it was last read.
>
> If you're interested in tackling this, I can sketch it out for you :)
I'm definitely interested in helping out if I can, although there's a slight
risk of biting off more than I can chew: I probably understand even less
about the design and structure of your fs at the moment than you think!
I don't want to be a slow-moving obstacle on your critical path or more of a
nuisance than a help, but equally, getting stuck in is clearly the best way
to figure out how it fits together and become more useful. So happy to give
anything a go that you think is reasonable for a newcomer to take a crack
at. :)
Best wishes,
Chris.
next prev parent reply other threads:[~2021-11-06 21:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-06 17:11 More eager discard behaviour Chris Webb
2021-11-06 19:37 ` Kent Overstreet
2021-11-06 21:36 ` Chris Webb [this message]
2021-11-07 14:59 ` Kent Overstreet
2021-11-08 21:16 ` Chris Webb
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=20211106213649.GN11670@arachsys.com \
--to=chris@arachsys.com \
--cc=kent.overstreet@gmail.com \
--cc=linux-bcachefs@vger.kernel.org \
/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).