Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Wed, 2 Nov 2022 14:36:35 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     Sergey Senozhatsky <senozhatsky@chromium.org>
Cc:     Nhat Pham <nphamcs@gmail.com>, akpm@linux-foundation.org,
        hannes@cmpxchg.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, ngupta@vflare.org,
        sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com
Subject: Re: [PATCH 2/5] zsmalloc: Consolidate zs_pool's migrate_lock and
 size_class's locks
Message-ID: <Y2Li412OGB6g8ARA@google.com>
References: <20221026200613.1031261-1-nphamcs@gmail.com>
 <20221026200613.1031261-3-nphamcs@gmail.com>
 <Y2Hj+H4VzlN/fcmR@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Y2Hj+H4VzlN/fcmR@google.com>
Precedence: bulk

On Wed, Nov 02, 2022 at 12:28:56PM +0900, Sergey Senozhatsky wrote:
> On (22/10/26 13:06), Nhat Pham wrote:
> >  struct size_class {
> > -	spinlock_t lock;
> >  	struct list_head fullness_list[NR_ZS_FULLNESS];
> >  	/*
> >  	 * Size of objects stored in this class. Must be multiple
> > @@ -247,8 +245,7 @@ struct zs_pool {
> >  #ifdef CONFIG_COMPACTION
> >  	struct work_struct free_work;
> >  #endif
> > -	/* protect page/zspage migration */
> > -	rwlock_t migrate_lock;
> > +	spinlock_t lock;
> >  };
> 
> I'm not in love with this, to be honest. One big pool lock instead
> of 255 per-class locks doesn't look attractive, as one big pool lock
> is going to be hammered quite a lot when zram is used, e.g. as a regular
> block device with a file system and is under heavy parallel writes/reads.
> 
I agree with Sergey.

I am also worry about that LRU stuff should be part of allocator
instead of higher level.