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56 lines
2.3 KiB
Diff
56 lines
2.3 KiB
Diff
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From 9706327002caebe6633c93e605882ea37172ec57 Mon Sep 17 00:00:00 2001
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From: Andres Salomon <dilinger@debian.org>
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Date: Mon, 3 Nov 2008 01:08:25 +0000
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Subject: [PATCH] jffs2-choke-gc-thread.patch
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I've noticed some pretty poor behavior on OLPC machines after bootup, when
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gdm/X are starting. The GCD monopolizes the scheduler (which in turns means
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it gets to do more nand i/o), which results in processes taking much much
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longer than they should to start.
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As an example, on an OLPC machine going from OFW to a usable X (via auto-login
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gdm) takes 2m 30s. The majority of this time is consumed by the switch into
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graphical mode. With this patch, we cut a full 60s off of bootup time. After
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bootup, things are much snappier as well.
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Note that we have seen a CRC node error with this patch that causes the machine
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to fail to boot, but we've also seen that problem without this patch.
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Signed-off-by: Andres Salomon <dilinger@debian.org>
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---
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fs/jffs2/background.c | 18 +++++++++++-------
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1 files changed, 11 insertions(+), 7 deletions(-)
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diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
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index 8adebd3..f38d557 100644
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--- a/fs/jffs2/background.c
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+++ b/fs/jffs2/background.c
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@@ -95,13 +95,17 @@ static int jffs2_garbage_collect_thread(void *_c)
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schedule();
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}
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- /* This thread is purely an optimisation. But if it runs when
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- other things could be running, it actually makes things a
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- lot worse. Use yield() and put it at the back of the runqueue
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- every time. Especially during boot, pulling an inode in
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- with read_inode() is much preferable to having the GC thread
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- get there first. */
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- yield();
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+ /* Problem - immediately after bootup, the GCD spends a lot
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+ * of time in places like jffs2_kill_fragtree(); so much so
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+ * that userspace processes (like gdm and X) are starved
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+ * despite plenty of cond_resched()s and renicing. Yield()
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+ * doesn't help, either (presumably because userspace and GCD
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+ * are generally competing for a higher latency resource -
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+ * disk).
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+ * This forces the GCD to slow the hell down. Pulling an
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+ * inode in with read_inode() is much preferable to having
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+ * the GC thread get there first. */
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+ schedule_timeout_interruptible(msecs_to_jiffies(50));
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/* Put_super will send a SIGKILL and then wait on the sem.
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*/
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--
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1.5.6.5
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