linux-kernel - Re: WIP: Performance improvements

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Date:   Fri, 28 Jul 2023 13:13:05 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc:     Michał Mirosław <emmir@...gle.com>,
        Paul Gofman <pgofman@...eweavers.com>,
        Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrei Vagin <avagin@...il.com>,
        Danylo Mocherniuk <mdanylo@...gle.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Mike Rapoport <rppt@...nel.org>, Nadav Amit <namit@...are.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Yang Shi <shy828301@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Yun Zhou <yun.zhou@...driver.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Alex Sierra <alex.sierra@....com>,
        Matthew Wilcox <willy@...radead.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        kernel@...labora.com,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Subject: Re: WIP: Performance improvements

On Fri, Jul 28, 2023 at 04:02:02PM +0500, Muhammad Usama Anjum wrote:
> We are optimizing for more performance. Please find the change-set below
> for easy review before next revision and post your comments:
> 
> - Replace memcpy() with direct copy as it proving to be very expensive
> - Don't check if PAGE_IS_FILE if no mask needs it as it is very
>   expensive to check per pte
> - Add question in comment for discussion purpose
> - Add fast path for exclusive WP for ptes

Please read the kernel documentation for how to properly submit patches
(i.e. don't mush them all together into one and then properly describe
what you are doing and why you are doing it).

Also actually test the patch and prove (or disprove) if it does matter
for performance.

good luck!

greg k-h