RE: Always cache?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Okay, I will give that a try now.

I thought write through caused immediate write to backing device though?  Maybe I understood it wrong.

Will confirm either way.

Cheers,

James

-----Original Message-----
From: Kent Overstreet [mailto:koverstreet@xxxxxxxxxx] 
Sent: 03 November 2012 22:41
To: James Sefton
Cc: linux-bcache@xxxxxxxxxxxxxxx
Subject: Re: Always cache?

Hey - set cache_mode to writethrough, and then if you really want everything to hit the cache, also set both congested_thresholds to 0

On Sat, Nov 3, 2012 at 11:53 AM, James Sefton <james@xxxxxxxxxxxx> wrote:
> Hi Kent,
>
> I am trying to configure the cache to always cache.
> The only time I want it to bypass the cache is when it has to.  (ie.. 
> cache
> full)
>
> In particular - I want all writes to hit the writeback cache and never 
> be written directly. (Unless no space is left for writeback)
>
> I am not sure how to configure this.  I thought I had done it once 
> before but I cant seem to reproduce it.
>
> Here are my settings so far:
>
> /sys/block/bcache0/bcache/
>
> cache_mode = writethrough [writeback] writearound none readahead = 0 
> running = 1 sequential_cutoff = 0 (also tried this at 1.1G, which 
> appears to be maximum) sequential_merge = 1 (also tried 0.  I have no 
> idea what this means) state = clean writeback_delay = 30 
> writeback_metadata = 1 (not sure what this does) writeback_percent = 
> 40 (also tried at 10) writeback_running = 1
>
>
> not sure what else there is to configure.
> Any suggestions would be appreciated.
>
> I am basically trying to maintain responsive disk access as much as possible.
> The backing storage is on a slow link to a SAN and when accessed 
> directly is relatively slow.  I want it to use the cache as much as is 
> possible and then bCache write the cache data to the backend storage 
> behind the scenes.  Workload is mixed..  random and sequential reads 
> and writes, anything from just a few bytes to 4-5Gb files.
>
> I am guessing that sequential_cutoff = 0 disables the cut-off feature.  
> (I tried the max of 1.1G too, just in case)
>
> I am using nmon to monitor where data is being written while copying /usr into
> the filesystem on cache0p1. (ext4)   I am seeing writes going to the cache
> device and the backing device simultaneously - but the cache is not 
> written to heavily.  Performance seen when copying is similar to that 
> of if I was just writing to the backing device directly.  (maybe a 
> little better since some bits are getting written to the cache)
>
> Any suggestion what I may be doing wrong?
>
> Cheers,
>
> James
>
> --
> To unsubscribe from this list: send the line "unsubscribe 
> linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx 
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-bcache" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux ARM Kernel]     [Linux Filesystem Development]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Security]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux