Messages in this thread | | | Date | Fri, 02 Mar 2007 10:26:25 +0900 | From | Tomoki Sekiyama <> | Subject | Re: [RFC][PATCH 0/3] VM throttling: avoid blocking occasional writers |
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Hi Kamezawa-san,
KAMEZAWA Hiroyuki wrote: >>> >>> Interesting, but how about adjust this parameter like below instead of >>> >>> adding new control knob ?(this kind of knob is not easy to use.) <snip> >>> >>> count_dirty_pages_on_device_limited(bdi, writechunk) above returns >>> >>> dirty pages on bdi. if # of dirty_pages on bdi is larger than writechunk, >>> >>> just returns writechunk. >> >> >> >> I think that way is not enough to control the total amount of >> >> Dirty+Writeback. >> >> >> >> In that way, while writeback_inodes() scans for dirty pages and writes >> >> them back, the caller will be blocked only if the length of the write- >> >> requests queue is longer than nr_requests.
> > What nr_request means ?
nr_requests is a parameter that means upper limit of the length of I/O (read- and write-)requests queue of the device, which is configurable from /sys/block/<device>/queue/nr_requests. A process, which perform I/O when there are more than nr_requests requests in the queue, will be blocked.
> > But Ok, maybe I'm not understanding. What I want to ask you is do > > per-device-write-throttling rather than adding a new parameter.
In the patchset, per-device-write-throttling is done by the behavior of the write-requests queue described above.
When the queue of the disk becomes full while writeback of Dirty in writeback_inodes(), heavy writes to the disk will be blocked. In contrast, if it's so occasional that the queue doesn't become full, writes will not be blocked.
Regards -- Tomoki Sekiyama Hitachi, Ltd., Systems Development Laboratory - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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