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Tue, 15 Apr 2025 14:38:46 +0000 (UTC) Date: Tue, 15 Apr 2025 22:38:38 +0800 From: Baoquan He To: "Uladzislau Rezki (Sony)" Cc: Andrew Morton , linux-mm@kvack.org, LKML , Christoph Hellwig , Oleksiy Avramchenko Subject: Re: [PATCH] vmalloc: Use atomic_long_add_return_relaxed() Message-ID: References: <20250415112646.113091-1-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250415112646.113091-1-urezki@gmail.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 X-Rspamd-Queue-Id: 2023520013 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: nzmq7wedmysm3jwj9uk1f89ckt6or1cn X-HE-Tag: 1744727933-226890 X-HE-Meta: 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 KBCIX/YD 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 04/15/25 at 01:26pm, Uladzislau Rezki (Sony) wrote: > Switch from the atomic_long_add_return() to its relaxed version. > > We do not need a full memory barrier or any memory ordering during > increasing the "vmap_lazy_nr" variable. What we only need is to do it > atomically. This is what atomic_long_add_return_relaxed() guarantees. > > AARCH64: > > > Default: > 40ec: d34cfe94 lsr x20, x20, #12 > 40f0: 14000044 b 4200 > 40f4: 94000000 bl 0 <__sanitizer_cov_trace_pc> > 40f8: 90000000 adrp x0, 0 <__traceiter_alloc_vmap_area> > 40fc: 91000000 add x0, x0, #0x0 > 4100: f8f40016 ldaddal x20, x22, [x0] > 4104: 8b160296 add x22, x20, x22 > > Relaxed: > 40ec: d34cfe94 lsr x20, x20, #12 > 40f0: 14000044 b 4200 > 40f4: 94000000 bl 0 <__sanitizer_cov_trace_pc> > 40f8: 90000000 adrp x0, 0 <__traceiter_alloc_vmap_area> > 40fc: 91000000 add x0, x0, #0x0 > 4100: f8340016 ldadd x20, x22, [x0] > 4104: 8b160296 add x22, x20, x22 > > > Signed-off-by: Uladzislau Rezki (Sony) > --- > mm/vmalloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 7bb32f498d39..9d4027041a3f 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2370,7 +2370,7 @@ static void free_vmap_area_noflush(struct vmap_area *va) > if (WARN_ON_ONCE(!list_empty(&va->list))) > return; > > - nr_lazy = atomic_long_add_return(va_size(va) >> PAGE_SHIFT, > + nr_lazy = atomic_long_add_return_relaxed(va_size(va) >> PAGE_SHIFT, > &vmap_lazy_nr); LGTM, Reviewed-by: Baoquan He