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;
Message-ID: <e8e85d7d-edf1-7a8b-8cfe-9976dd9cfb0b@quicinc.com>
Date:   Thu, 18 May 2023 18:16:25 +0530
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.9.1
Subject: Re: [PATCH V7 2/2] mm: shmem: implement POSIX_FADV_[WILL|DONT]NEED
 for shmem
Content-Language: en-US
To:     Hugh Dickins <hughd@google.com>
CC:     <akpm@linux-foundation.org>, <willy@infradead.org>,
        <markhemm@googlemail.com>, <rientjes@google.com>,
        <surenb@google.com>, <shakeelb@google.com>, <fvdl@google.com>,
        <quic_pkondeti@quicinc.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>
References: <cover.1676378702.git.quic_charante@quicinc.com>
 <631e42b6dffdcc4b4b24f5be715c37f78bf903db.1676378702.git.quic_charante@quicinc.com>
 <2d56e1dd-68b5-c99e-522f-f8dadf6ad69e@google.com>
 <eeeba374-9247-96fd-c9f5-8cba8761f1b9@quicinc.com>
 <aa4352d8-a549-32e5-874f-1cfee2a5b3e@google.com>
From:   Charan Teja Kalla <quic_charante@quicinc.com>
In-Reply-To: <aa4352d8-a549-32e5-874f-1cfee2a5b3e@google.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi Hugh, Thanks for the time and comments on this patch.

On 5/17/2023 5:02 PM, Hugh Dickins wrote:
>> Sure, will include those range calculations for shmem pages too.
> Oh, I forgot this issue, you would have liked me to look at V8 by now,
> to see whether I agree with your resolution there.  Sorry, no, I've
> not been able to divert my concentration to it yet.
> 
> And it's quite likely that I shall disagree, because I've a history of
> disagreeing even with myself on such range widening/narrowing issues -
> reconciling conflicting precedents is difficult :(
> 
If you can at least help by commenting which part of the patch you
disagree with, I can try hard to convince you there:) .

>> Please let me know if I'm missing something where I should be counting
>> these as NR_ISOLATED.
> Please grep for NR_ISOLATED, to see where and how they get manipulated
> already, and follow the existing examples.  The case that sticks in my
> mind is in mm/mempolicy.c, where the migrate_pages() syscall can build
> up a gigantic quantity of transiently isolated pages: your syscall can
> do the same, so should account for itself in the same way.

I had a V8 posted without this into accounting. Let me make the changes
to account for the NR_ISOLATED too.
> 
> I'm not claiming that mm/vmscan.c's too_many_isolated(), and the way it
> gets used by shrink_inactive_list(), is perfect: not at all.  But please
> follow existing convention.
> 
> Sorry, that's all for now.