From: Ingo Molnar <mingo@elte.hu>
To: Hugh Dickins <hugh@veritas.com>
Cc: Andrew Morton <akpm@osdl.org>, Andrea Arcangeli <andrea@suse.de>,
Rajesh Venkatasubramanian <vrajesh@umich.edu>,
Lorenzo Allegrucci <l_allegrucci@yahoo.it>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/6] vmtrunc: restore unmap_vmas zap_bytes
Date: Sun, 3 Oct 2004 20:36:12 +0200 [thread overview]
Message-ID: <20041003183612.GA29653@elte.hu> (raw)
In-Reply-To: <Pine.LNX.4.44.0410031923390.2755-100000@localhost.localdomain>
* Hugh Dickins <hugh@veritas.com> wrote:
> The low-latency unmap_vmas patch silently moved the zap_bytes test
> after the TLB finish and lockbreak and regather: why? That not only
> makes zap_bytes redundant (might as well use ZAP_BLOCK_SIZE), it makes
> the unmap_vmas level redundant too - it's all about saving TLB flushes
> when unmapping a series of small vmas.
the problem was latency generated by pages queueing up in tlb_gather's
queue and being freed in one loop, causing latencies. So there was no
latency-break, only a shifting of the queue.
> Move zap_bytes test back before the lockbreak, and delete the curious
> comment that a small zap block size doesn't matter: it's true
> need_flush prevents TLB flush when no page has been unmapped, but
> unmapping pages in small blocks involves many more TLB flushes than in
> large blocks.
could we perhaps free those pages outside of the lock? That would be
just as good for me.
Ingo
next prev parent reply other threads:[~2004-10-03 18:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-03 18:21 [PATCH 0/6] vmtrunc: lowlat vmtruncate drop i_mmap_lock Hugh Dickins
2004-10-03 18:23 ` [PATCH 1/6] vmtrunc: truncate_count not atomic Hugh Dickins
2004-10-03 18:24 ` [PATCH 2/6] vmtrunc: restore unmap_vmas zap_bytes Hugh Dickins
2004-10-03 18:36 ` Ingo Molnar [this message]
2004-10-03 18:25 ` [PATCH 3/6] vmtrunc: unmap_mapping_range_tree Hugh Dickins
2004-10-03 18:26 ` [PATCH 4/6] vmtrunc: unmap_mapping dropping i_mmap_lock Hugh Dickins
2004-10-03 18:27 ` [PATCH 5/6] vmtrunc: vm_truncate_count race caution Hugh Dickins
2004-10-03 18:28 ` [PATCH 6/6] vmtrunc: bug if page_mapped Hugh Dickins
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