linux-kernel - Re: [PATCHv2 5/6] zsmalloc: extend compaction statistics

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Message-ID: <Y/5+PEfuEl3b/sDR@google.com>
Date:   Tue, 28 Feb 2023 14:20:44 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv2 5/6] zsmalloc: extend compaction statistics

On Sun, Feb 26, 2023 at 12:55:45PM +0900, Sergey Senozhatsky wrote:
> On (23/02/23 15:51), Minchan Kim wrote:
> > On Thu, Feb 23, 2023 at 12:04:50PM +0900, Sergey Senozhatsky wrote:
> > > Extend zsmalloc zs_pool_stats with a new member that
> > > holds the number of objects pool compaction moved
> > > between pool pages.
> > 
> > I totally understand this new stat would be very useful for your
> > development but not sure it's really useful for workload tune or
> > monitoring.
> > 
> > Unless we have strong usecase, I'd like to avoid new stat.
> 
> The way I see is that it *can* give some interesting additional data to
> periodical compaction (the one is not triggeed by the shrinker): if the
> number of moves objects is relatively high but the number of comapcted
> (feeed) pages is relatively low then the system has fragmentation in
> small size classes (that tend to have many objects per zspage but not
> too many pages per zspage) and in this case the interval between
> periodical compactions probably can be increased. What do you think?

In the case, how could we get only data triggered by periodical munual
compaction?