Messages in this thread | | | Date | Fri, 05 Apr 2002 11:58:16 -0800 | From | Andrew Morton <> | Subject | Re: Report: 2.4.18 very high latencies (with lowlat. and pre-empt patches) |
| |
Ricardo Galli wrote: > > 1. Put ten (10) to twenty (20) files of 64-80 MB each in computer B. For > example in /tmp/test. > > 2. Mount in B a disk in A via NFS in, for example, /mnt/A > > 3. In B, run the following command: > cp /tmp/test/* /mnt/A > > 4. Check in A how you mouse freezes. >
You're writing a large amount of data to disk. Presumably the X server on the same machine wants to read a little bit of data from the same disk. The X server spends a long time in disk wait, behind all the writes.
This is somewhat worsened by the VM's tendency to evict useful pages in favour of less useful pages (cache for large reads and writes).
You will probably find that the -aa VM will help a little, by reducing the tendency to evict the wrong pages. You will probably find that http://www.zip.com.au/~akpm/linux/patches/2.4/2.4.18-pre1/read-latency2.patch helps a lot, by allowing the reads to be satisfied more quickly.
You will probably find that current -ac kernels help a lot, because they contain read-latency2. -ac kernels also have a different VM which I think makes an attempt to special-case the large streaming read and write problem.
We're getting there, slowly.
- - 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/
| |