Just wondering, when I remove a 128MB file on vfat partition
(usb-storage, memcard reader), it causes 54.6ms latency
in rtc_latencytest... latency seems to increase linearly
as the filesize grows. I calculated 1s would be reached with
2344MB file but I didn't bother trying that yet.
Are there any possible fixes for fat fs so
that it doesn't disable interrupts for that long a time?
When I use loop device (the file on reiserfs), I get 45.9ms latency,
so this is not usb's fault.
These with Linux-2.6.10-ac8 on UP, PPro+, no preempt.
http://safari.iki.fi/vfat-unlink/
--
Sami Farin <[email protected]> writes:
> Just wondering, when I remove a 128MB file on vfat partition
> (usb-storage, memcard reader), it causes 54.6ms latency
> in rtc_latencytest... latency seems to increase linearly
> as the filesize grows. I calculated 1s would be reached with
> 2344MB file but I didn't bother trying that yet.
> Are there any possible fixes for fat fs so
> that it doesn't disable interrupts for that long a time?
The fatfs itself doesn't disable any interrupt. I guess the thing
depending on file size is the fat_free().
So, the following patch may change the behavior...
--
OGAWA Hirofumi <[email protected]>
diff -up linux-2.6.10/fs/fat/cache.c.orig linux-2.6.10/fs/fat/cache.c
--- linux-2.6.10/fs/fat/cache.c.orig 2004-12-25 06:35:24.000000000 +0900
+++ linux-2.6.10/fs/fat/cache.c 2005-01-11 03:34:54.000000000 +0900
@@ -491,6 +491,8 @@ int fat_free(struct inode *inode, int sk
if (MSDOS_SB(sb)->free_clusters != -1)
MSDOS_SB(sb)->free_clusters++;
inode->i_blocks -= MSDOS_SB(sb)->cluster_size >> 9;
+
+ cond_resched();
} while (nr != FAT_ENT_EOF);
fat_clusters_flush(sb);
nr = 0;
On Tue, Jan 11, 2005 at 03:38:32AM +0900, OGAWA Hirofumi wrote:
> Sami Farin <[email protected]> writes:
>
> > Just wondering, when I remove a 128MB file on vfat partition
> > (usb-storage, memcard reader), it causes 54.6ms latency
> > in rtc_latencytest... latency seems to increase linearly
> > as the filesize grows. I calculated 1s would be reached with
> > 2344MB file but I didn't bother trying that yet.
> > Are there any possible fixes for fat fs so
> > that it doesn't disable interrupts for that long a time?
>
> The fatfs itself doesn't disable any interrupt. I guess the thing
> depending on file size is the fat_free().
>
> So, the following patch may change the behavior...
> --
> OGAWA Hirofumi <[email protected]>
>
> diff -up linux-2.6.10/fs/fat/cache.c.orig linux-2.6.10/fs/fat/cache.c
> --- linux-2.6.10/fs/fat/cache.c.orig 2004-12-25 06:35:24.000000000 +0900
> +++ linux-2.6.10/fs/fat/cache.c 2005-01-11 03:34:54.000000000 +0900
> @@ -491,6 +491,8 @@ int fat_free(struct inode *inode, int sk
> if (MSDOS_SB(sb)->free_clusters != -1)
> MSDOS_SB(sb)->free_clusters++;
> inode->i_blocks -= MSDOS_SB(sb)->cluster_size >> 9;
> +
> + cond_resched();
> } while (nr != FAT_ENT_EOF);
> fat_clusters_flush(sb);
> nr = 0;
Oh yeah, now max latency is around 1.5ms.
Thanks for the patch.
--
On Tue, 11 Jan 2005, OGAWA Hirofumi wrote:
> Sami Farin <[email protected]> writes:
>
>> Just wondering, when I remove a 128MB file on vfat partition
>> (usb-storage, memcard reader), it causes 54.6ms latency
>> in rtc_latencytest... latency seems to increase linearly
>> as the filesize grows. I calculated 1s would be reached with
>> 2344MB file but I didn't bother trying that yet.
>> Are there any possible fixes for fat fs so
>> that it doesn't disable interrupts for that long a time?
>
> The fatfs itself doesn't disable any interrupt. I guess the thing
> depending on file size is the fat_free().
>
> So, the following patch may change the behavior...
diff -up linux-2.6.10/fs/fat/cache.c.orig linux-2.6.10/fs/fat/cache.c
--- linux-2.6.10/fs/fat/cache.c.orig 2004-12-25 06:35:24.000000000 +0900
+++ linux-2.6.10/fs/fat/cache.c 2005-01-11 03:34:54.000000000 +0900
@@ -491,6 +491,8 @@ int fat_free(struct inode *inode, int sk
if (MSDOS_SB(sb)->free_clusters != -1)
MSDOS_SB(sb)->free_clusters++;
inode->i_blocks -= MSDOS_SB(sb)->cluster_size >> 9;
+
+ cond_resched();
} while (nr != FAT_ENT_EOF);
fat_clusters_flush(sb);
nr = 0;
-
Thanks for your patchset.tar (in another thread) from:
Thu, 30 Dec 2004 12:02:14 +0900.
Based on the patch above, is an additional cond_resched() call required
somewhere in your 2004/12/30 patchset?
In your 2004/12/30 patchset, if I am reading it correctly, fat_free seems to
have moved from cache.c to file.c and the code isn't similar enough for me
to see where a cond_resched() could be added.
Perhaps you have already have a newer patchset?
Thanks for your time.
Regards,
Rob
--
---------------------"Happiness is understanding."----------------------
Robert Hardy, B.Eng Computer Systems C.E.O. Webcon Inc.
rhardy <at> webcon <dot> ca GPG Key available (613) 276-7327
Robert Hardy <[email protected]> writes:
> Thanks for your patchset.tar (in another thread) from:
> Thu, 30 Dec 2004 12:02:14 +0900.
>
> Based on the patch above, is an additional cond_resched() call required
> somewhere in your 2004/12/30 patchset?
>
> In your 2004/12/30 patchset, if I am reading it correctly, fat_free seems to
> have moved from cache.c to file.c and the code isn't similar enough for me
> to see where a cond_resched() could be added.
Yes. For that patchset, need to add the similar code to
fat_free_cluster() in fs/fat/fatent.c.
err = fat_write_entry(sb, &fatent, FAT_ENT_FREE);
if (err)
goto error;
if (sbi->free_clusters != -1)
sbi->free_clusters++;
cond_resched(); <--- add this line
} while (cluster != FAT_ENT_EOF);
> Perhaps you have already have a newer patchset?
Yes. I added the 8~10 patches to patchset. However, current patchset
can't compile temporarily. Sorry. Please wait for next weekend.
--
OGAWA Hirofumi <[email protected]>