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;
Date:   Fri, 14 Apr 2023 11:34:03 +0200 (CEST)
From:   Miroslav Benes <mbenes@suse.cz>
To:     Luis Chamberlain <mcgrof@kernel.org>
cc:     david@redhat.com, patches@lists.linux.dev,
        linux-modules@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, pmladek@suse.com,
        petr.pavlu@suse.com, prarit@redhat.com,
        torvalds@linux-foundation.org, gregkh@linuxfoundation.org,
        rafael@kernel.org, christophe.leroy@csgroup.eu, tglx@linutronix.de,
        peterz@infradead.org, song@kernel.org, rppt@kernel.org,
        dave@stgolabs.net, willy@infradead.org, vbabka@suse.cz,
        mhocko@suse.com, dave.hansen@linux.intel.com,
        colin.i.king@gmail.com, jim.cromie@gmail.com,
        catalin.marinas@arm.com, jbaron@akamai.com,
        rick.p.edgecombe@intel.com
Subject: Re: [PATCH v3 2/2] modules/kmod: replace implementation with a
 semaphore
In-Reply-To: <20230414051349.1986744-3-mcgrof@kernel.org>
Message-ID: <alpine.LSU.2.21.2304141133530.4426@pobox.suse.cz>
References: <20230414051349.1986744-1-mcgrof@kernel.org> <20230414051349.1986744-3-mcgrof@kernel.org>
User-Agent: Alpine 2.21 (LSU 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Thu, 13 Apr 2023, Luis Chamberlain wrote:

> Simplify the concurrency delimiter we use for kmod with the semaphore.
> I had used the kmod strategy to try to implement a similar concurrency
> delimiter for the kernel_read*() calls from the finit_module() path
> so to reduce vmalloc() memory pressure. That effort didn't provide yet
> conclusive results, but one thing that became clear is we can use
> the suggested alternative solution with semaphores which Linus hinted
> at instead of using the atomic / wait strategy.
> 
> I've stress tested this with kmod test 0008:
> 
> time /data/linux-next/tools/testing/selftests/kmod/kmod.sh -t 0008
> 
> And I get only a *slight* delay. That delay however is small, a few
> seconds for a full test loop run that runs 150 times, for about ~30-40
> seconds. The small delay is worth the simplfication IMHO.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

Reviewed-by: Miroslav Benes <mbenes@suse.cz>

M