archive mirror
 help / color / mirror / Atom feed
From: Andrew Morton <>
To: Vitaly Wool <>
Cc: Linux-MM <>,
	LKML <>,, Guenter Roeck <>
Subject: Re: [PATCH] z3fold: encode object length in the handle
Date: Wed, 7 Nov 2018 15:00:52 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Mon, 29 Oct 2018 13:27:36 +0100 Vitaly Wool <> wrote:

> Hi Andrew,
> Den tors 25 okt. 2018 kl 21:42 skrev Andrew Morton <
> > On Thu, 25 Oct 2018 11:28:21 +0200 Vitaly Wool <>
> > wrote:
> >
> > > Reclaim and free can race on an object (which is basically ok) but
> > > in order for reclaim to be able to  map "freed" object we need to
> > > encode object length in the handle. handle_to_chunks() is thus
> > > introduced to extract object length from a handle and use it during
> > > mapping of the last object we couldn't correctly map before.
> >
> > What are the runtime effects of this change?
> >
> I haven't observed any adverse impact with this change used in zswap (and
> in fact, this is a bugfix for zswap operation). There is a slight under 1%
> impact when z3fold is used with ZRAM but since the support for ZRAM over
> zpool is still out of tree, I take it doesn't matter at this point, right?

I mean "runtime effects", not "run time effects" ;)

Apart from wishing to document this change fully, I'm trying to
understand which kernel version(s) need the fix.  To understand that, I
need to know the effect upon end-user-visible behaviour.  You say it
fixes a bug - please describe that bug: how it is triggered, what
effect is has, etc.

Also, any suggestions as to which kernel versions we should fix is
always welcome.

      parent reply	other threads:[~2018-11-07 23:00 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-25  9:28 Vitaly Wool
2018-10-25 19:42 ` Andrew Morton
     [not found]   ` <>
2018-11-07 23:00     ` Andrew Morton [this message]

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \
    --subject='Re: [PATCH] z3fold: encode object length in the handle' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

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).