Re: [RFC][PATCH 5/7] writeback: use 64MB MAX_WRITEBACK_PAGES

Peter Zijlstra
2009-09-10T04:53:50Z

On Wed, 2009-09-09 at 19:29 -0400, Theodore Tso wrote:
> On Wed, Sep 09, 2009 at 10:51:46PM +0800, Wu Fengguang wrote:
> > + * The maximum number of pages to writeout in a single periodic/background
> > + * writeback operation. 64MB means I_SYNC may be hold for up to 1 second.
> > + * This is not a big problem since we normally do kind of trylock on I_SYNC
> > + * for non-data-integrity writes. Userspace tasks doing throttled writeback
> > + * do not use this value.
>
> What's your justification for using 64MB? Where are you getting 1
> second from? On a fast RAID array 64MB can be written in much less
> than 1 second.

Worse, on my 5mb/s usb stick writing out 64m will take forever.