40 lines
1.3 KiB
Diff
40 lines
1.3 KiB
Diff
From 400ffe97d5db1a3a06de77851d44813ff48ebb9a Mon Sep 17 00:00:00 2001
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From: root <root@localhost.localdomain>
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Date: Wed, 13 Mar 2019 11:27:13 +0800
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Subject: [PATCH 02/17] bcache: reduce MAX_IO to 256
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This is the number of concurrent async io requests that
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the scan layer will submit to the bcache layer. There
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will be an open fd for each of these, so it is best to
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keep this well below the default limit for max open files
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(1024), otherwise lvm may get EMFILE from open(2) when
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there are around 1024 devices to scan on the system.
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---
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lib/device/bcache.c | 10 +++++++++-
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1 file changed, 9 insertions(+), 1 deletion(-)
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diff --git a/lib/device/bcache.c b/lib/device/bcache.c
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index b1f7d2a..531d83b 100644
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--- a/lib/device/bcache.c
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+++ b/lib/device/bcache.c
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@@ -196,7 +196,15 @@ static bool _async_issue(struct io_engine *ioe, enum dir d, int fd,
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return true;
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}
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-#define MAX_IO 1024
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+/*
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+ * MAX_IO is returned to the layer above via bcache_max_prefetches() which
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+ * tells the caller how many devices to submit io for concurrently. There will
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+ * be an open file descriptor for each of these, so keep it low enough to avoid
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+ * reaching the default max open file limit (1024) when there are over 1024
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+ * devices being scanned.
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+ */
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+
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+#define MAX_IO 256
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#define MAX_EVENT 64
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static bool _async_wait(struct io_engine *ioe, io_complete_fn fn)
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--
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2.19.1
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