Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 3 Jun 2020 12:08:28 -0400
From:   Daniel Jordan <daniel.m.jordan@oracle.com>
To:     Anshuman Khandual <anshuman.khandual@arm.com>
Cc:     Daniel Jordan <daniel.m.jordan@oracle.com>,
        John Hubbard <jhubbard@nvidia.com>, linux-mm@kvack.org,
        hughd@google.com, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Zi Yan <ziy@nvidia.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/vmstat: Add events for PMD based THP migration
 without split
Message-ID: <20200603160828.2sfuyjpyyc2bpuan@ca-dmjordan1.us.oracle.com>
References: <1590118444-21601-1-git-send-email-anshuman.khandual@arm.com>
 <20200601165736.qw5kwwknxltk7bv6@ca-dmjordan1.us.oracle.com>
 <0a936ec7-f44f-1d72-915f-f5758d25fd72@nvidia.com>
 <1e71d815-5359-3ebe-5d2b-5a3b54b63b51@arm.com>
 <274be3bf-2206-5e98-8114-1d91fac472c9@nvidia.com>
 <20200602145208.qucum52lwslhiqff@ca-dmjordan1.us.oracle.com>
 <db50792c-ced5-a59d-0d94-e1520cf53715@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <db50792c-ced5-a59d-0d94-e1520cf53715@arm.com>
User-Agent: NeoMutt/20180716
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jun 03, 2020 at 10:06:31AM +0530, Anshuman Khandual wrote:
> Does this look okay and sufficient ?
> 
> --- a/Documentation/vm/page_migration.rst
> +++ b/Documentation/vm/page_migration.rst
> @@ -253,5 +253,20 @@ which are function pointers of struct address_space_operations.
>       PG_isolated is alias with PG_reclaim flag so driver shouldn't use the flag
>       for own purpose.
>  
> +Quantifying Migration
> +=====================
> +Following events can be used to quantify page migration.
> +
> +- PGMIGRATE_SUCCESS
> +- PGMIGRATE_FAIL
> +- THP_MIGRATION_SUCCESS
> +- THP_MIGRATION_FAILURE
> +
> +THP_MIGRATION_FAILURE in particular represents an event when a THP could not be
> +migrated as a single entity following an allocation failure and ended up getting
> +split into constituent normal pages before being retried. This event, along with
> +PGMIGRATE_SUCCESS and PGMIGRATE_FAIL will help in quantifying and analyzing THP
> +migration events including both success and failure cases.

Looks great!

> Sure, will update the commit message accordingly.

Thanks.  Hopefully these will help someone in the future.