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Am 13.08.2012 20:18, schrieb Michael Hampicke: |
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> Am 13.08.2012 19:14, schrieb Florian Philipp: |
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>> Am 13.08.2012 16:52, schrieb Michael Mol: |
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>>> On Mon, Aug 13, 2012 at 10:42 AM, Michael Hampicke |
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>>> <mgehampicke@×××××.com <mailto:mgehampicke@×××××.com>> wrote: |
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>>> |
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>>> Have you indexed your ext4 partition? |
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>>> |
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>>> # tune2fs -O dir_index /dev/your_partition |
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>>> # e2fsck -D /dev/your_partition |
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>>> |
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>>> Hi, the dir_index is active. I guess that's why delete operations |
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>>> take as long as they take (index has to be updated every time) |
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>>> |
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>>> |
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>>> 1) Scan for files to remove |
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>>> 2) disable index |
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>>> 3) Remove files |
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>>> 4) enable index |
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>>> |
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>>> ? |
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>>> |
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>>> -- |
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>>> :wq |
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>> |
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>> Other things to think about: |
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>> |
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>> 1. Play around with data=journal/writeback/ordered. IIRC, data=journal |
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>> actually used to improve performance depending on the workload as it |
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>> delays random IO in favor of sequential IO (when updating the journal). |
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>> |
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>> 2. Increase the journal size. |
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>> |
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>> 3. Take a look at `man 1 chattr`. Especially the 'T' attribute. Of |
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>> course this only helps after re-allocating everything. |
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>> |
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>> 4. Try parallelizing. Ext4 requires relatively few locks nowadays (since |
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>> 2.6.39 IIRC). For example: |
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>> find $TOP_DIR -mindepth 1 -maxdepth 1 -print0 | \ |
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>> xargs -0 -n 1 -r -P 4 -I '{}' find '{}' -type f |
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>> |
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>> 5. Use a separate device for the journal. |
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>> |
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>> 6. Temporarily deactivate the journal with tune2fs similar to MM's idea. |
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>> |
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>> Regards, |
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>> Florian Philipp |
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>> |
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> |
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> Trying out different journals-/options was already on my list, but the |
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> manpage on chattr regarding the T attribute is an interesting read. |
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> Definitely worth trying. |
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> |
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> Parallelizing multiple finds was something I already did, but the only |
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> thing that increased was the IO wait :) But now having read all the |
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> suggestions in this thread, I might try it again. |
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> |
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> Separate device for the journal is a good idea, but not possible atm |
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> (machine is abroad in a data center) |
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> |
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|
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Something else I just remembered. I guess it doesn't help you with your |
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current problem but it might come in handy when working with such large |
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cache dirs: I once wrote a script that sorts files by their starting |
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physical block. This improved reading them quite a bit (2 minutes |
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instead of 11 minutes for copying the portage tree). |
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|
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It's a terrible clutch, will probably fail when passing FS boundaries or |
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a thousand other oddities and requires root for some very scary |
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programs. I never had the time to finish an improved C version. Anyway, |
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maybe it helps you: |
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|
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#!/bin/bash |
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# |
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# Example below copies /usr/portage/* to /tmp/portage. |
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# Replace /usr/portage with the input directory. |
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# Replace `cpio` with whatever does the actual work. Input is a |
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# \0-delimited file list. |
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# |
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FIFO=/tmp/$(uuidgen).fifo |
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mkfifo "$FIFO" |
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find /usr/portage -type f -fprintf "$FIFO" 'bmap <%i> 0\n' -print0 | |
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tr '\n\0' '\0\n' | |
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paste <( |
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debugfs -f "$FIFO" /dev/mapper/vg-portage | |
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grep -E '^[[:digit:]]+' |
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) - | |
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sort -k 1,1n | |
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cut -f 2- | |
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tr '\n\0' '\0\n' | |
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cpio -p0 --make-directories /tmp/portage/ |
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unlink "$FIFO" |
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