Opened 14 years ago

Closed 14 years ago

#250 closed defect (fixed)

write operation slows down gradually when writing large amount of data.

Reported by: Tomas Brambora Owned by:
Priority: major Milestone: 0.4.3
Component: helenos/fs/fat Version: mainline
Keywords: Cc:
Blocker for: Depends on:
See also:


Writing a bug chunk of data (i.e. say 5MB) causes the write operation to gradually slow down. After a few minutes, the operation is at least 5x slower than at the beginning.

The operation finishes (after some time) successfully (I've tried writing 1 000 000 * sizeof(int))

Qemu 0.12.3, HelenOS compiled for IA32 dual core.

Attachments (1)

test_speed.c (1.0 KB ) - added by Tomas Brambora 14 years ago.
Test case for bug #250.

Download all attachments as: .zip

Change History (4)

comment:1 by Jakub Jermář, 14 years ago

We made an observation that creating a 5M file on a FAT file system using mkfile does not take that long - only about a minute and 20 seconds in Qemu on my laptop (and similar on Tomas' machine). Now we have two test cases that both go down to the FAT file system do about the same thing, but the one which writes less data lasts significantly longer than the other one.

comment:2 by Jakub Jermář, 14 years ago

In lp:~/jakub/helenos/fs there is a fix which improves the running time of the test cases by 50+% by caching the last cluster occupied by a FAT node.

by Tomas Brambora, 14 years ago

Attachment: test_speed.c added

Test case for bug #250.

comment:3 by Jakub Jermář, 14 years ago

Resolution: fixed
Status: newclosed

With changeset:mainline,624 comes a significant speedup of appending and other sequential I/O on the FAT filesystem, which fixes all known test cases to me. I am therefore closing this ticket as fixed.

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