From: Andy Lutomirski <luto@kernel.org>
To: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
sparclinux <sparclinux@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Network Development <netdev@vger.kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Nadav Amit <namit@vmware.com>,
"David S. Miller" <davem@davemloft.net>,
Rick Edgecombe <redgecombe.lkml@gmail.com>,
Meelis Roos <mroos@linux.ee>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH v2 2/2] vmalloc: Remove work as from vfree path
Date: Tue, 21 May 2019 09:17:32 -0700 [thread overview]
Message-ID: <CALCETrUdfBrTV3kMjdVHv2JDtEOGSkVvoV++96x4zjvue0GpZA@mail.gmail.com> (raw)
In-Reply-To: <20190520233841.17194-3-rick.p.edgecombe@intel.com>
On Mon, May 20, 2019 at 4:39 PM Rick Edgecombe
<rick.p.edgecombe@intel.com> wrote:
>
> From: Rick Edgecombe <redgecombe.lkml@gmail.com>
>
> Calling vm_unmap_alias() in vm_remove_mappings() could potentially be a
> lot of work to do on a free operation. Simply flushing the TLB instead of
> the whole vm_unmap_alias() operation makes the frees faster and pushes
> the heavy work to happen on allocation where it would be more expected.
> In addition to the extra work, vm_unmap_alias() takes some locks including
> a long hold of vmap_purge_lock, which will make all other
> VM_FLUSH_RESET_PERMS vfrees wait while the purge operation happens.
>
> Lastly, page_address() can involve locking and lookups on some
> configurations, so skip calling this by exiting out early when
> !CONFIG_ARCH_HAS_SET_DIRECT_MAP.
Hmm. I would have expected that the major cost of vm_unmap_aliases()
would be the flush, and at least informing the code that the flush
happened seems valuable. So would guess that this patch is actually a
loss in throughput.
--Andy
next prev parent reply other threads:[~2019-05-21 16:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-20 23:38 [PATCH v2 0/2] Fix issues with vmalloc flush flag Rick Edgecombe
2019-05-20 23:38 ` [PATCH v2 1/2] vmalloc: Fix calculation of direct map addr range Rick Edgecombe
2019-05-20 23:38 ` [PATCH v2 2/2] vmalloc: Remove work as from vfree path Rick Edgecombe
2019-05-21 16:17 ` Andy Lutomirski [this message]
2019-05-21 16:51 ` Edgecombe, Rick P
2019-05-21 17:00 ` Andy Lutomirski
2019-05-21 19:47 ` Edgecombe, Rick P
2019-05-20 23:46 ` [PATCH v2 0/2] Fix issues with vmalloc flush flag Edgecombe, Rick P
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