linux-kernel - Re: [PATCH v6 6/6] zsmalloc: Implement writeback mechanism for zsmalloc

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Message-ID: <Y3x109XxGY02Y7Vp@cmpxchg.org>
Date:   Tue, 22 Nov 2022 02:10:11 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Nhat Pham <nphamcs@...il.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        minchan@...nel.org, ngupta@...are.org, sjenning@...hat.com,
        ddstreet@...e.org, vitaly.wool@...sulko.com
Subject: Re: [PATCH v6 6/6] zsmalloc: Implement writeback mechanism for
 zsmalloc

On Tue, Nov 22, 2022 at 03:35:18PM +0900, Sergey Senozhatsky wrote:
> On (22/11/22 01:09), Johannes Weiner wrote:
> > On Tue, Nov 22, 2022 at 12:42:20PM +0900, Sergey Senozhatsky wrote:
> > > On (22/11/21 22:12), Johannes Weiner wrote:
> > > > On Tue, Nov 22, 2022 at 11:15:20AM +0900, Sergey Senozhatsky wrote:
> > > > > On (22/11/18 16:15), Nhat Pham wrote:
> 
> [..]
> 
> > > What I meant was: if zs_reclaim_page() makes only partial progress
> > > with the current LRU tail zspage and returns -EAGAIN, then we just
> > > don't increment `total` and continue looping in zs_zpool_shrink().
> > 
> > Hm, but it breaks on -EAGAIN, it doesn't continue.
> 
> Yes. "What if it would continue". Would it make sense to not
> break on EAGAIN?
> 
> 	while (total < pages) {
> 		ret = zs_reclaim_page(pool);
> 		if (ret == -EAGAIN)
> 			continue;
> 		if (ret < 0)
> 			break;
> 		total++;
> 	}
> 
> Then we don't need retry loop in zs_reclaim_page().

But that's an indefinite busy-loop?

I don't see what the problem with limited retrying in
zs_reclaim_page() is. It's robust and has worked for years.