please eat my data!

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+From: "Sebastian Spaeth" <Sebastian@SSpaeth.de>\r
+To: "Notmuch list" <notmuch@notmuchmail.org>\r
+Subject: please eat my data!\r
+Date: Mon, 12 Apr 2010 15:33:35 +0200\r
+Message-ID: <87633wlrrk.fsf@SSpaeth.de>\r
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+\r
+fsync is really killing xapian (and notmuch). What suffers, are the\r
+boolean prefixes (tag, id, and thread). Using libeatmydata (which\r
+disables fsync) shows a 10x speedup for tagging. The speedup is only\r
+factor 2 for e.g. from: searches. This is ext4 on recent stock\r
+Ubuntu. Given that search by tag and thread are performed really often\r
+(each time I advance a thread, for example), that really hurts.\r
+\r
+With a warm file cache and a thread containing 11 messages:\r
+\r
+---------------------------------------------------\r
+time notmuch tag +test -- thread:0000000000000f4e\r
+real   0m0.677s\r
+user   0m0.030s\r
+sys    0m0.020s\r
+---------------------------------------------------\r
+time LD_PRELOAD=./libeatmydata.so notmuch tag +test -- thread:0000000000000f4e\r
+\r
+real   0m0.040s\r
+user   0m0.020s\r
+sys    0m0.020s\r
+---------------------------------------------------\r
+\r
+However tagging ~850 messages based on a from search is "ONLY" factor 2:\r
+------------------------------------------------------\r
+time notmuch tag +test -- from:"sebastian@sspaeth.de"\r
+\r
+real   0m2.355s\r
+user   0m1.240s\r
+sys    0m0.040s\r
+---------------------------------------------------\r
+time LD_PRELOAD=./libeatmydata.so notmuch tag +test -- from:"sebastian@sspaeth.de"\r
+\r
+real   0m1.286s\r
+user   0m1.230s\r
+sys    0m0.010s\r
+---------------------------------------------------\r