Message ID | 1573731982-7370-1-git-send-email-frank.heimes@canonical.com |
---|---|
Headers | show |
Series | s390/dasd: reduce the default queue depth and nr of hardware queues (LP: 1852257) | expand |
On 2019-11-14 12:46:21 , frank.heimes@canonical.com wrote: > Buglink: https://bugs.launchpad.net/bugs/1852257 > > SRU Justification: > > [Impact] > > * On s390x systems with a small memory footprint, but large amounts of DASD disks, > > * the memory can get depleted (even during installation) and can eventually lead to a situation where the OOM kicks in (followed by even more problems). > > * Starting with kernel 4.18 the patch below leads to 90% memory consumption savings per active DASD device. > > * The below backport is needed to fix this and get the improvement into bionic's kernel 4.15. > > [Fix] > > * 3284da34a87ab7a527a593f89bbdaf6debe9e713 3284da3 "s390/dasd: reduce the default queue depth and nr of hardware queues" > > * Backport: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1852257/+attachment/5304830/+files/0001-s390-dasd-reduce-the-default-queue-depth-and-nr-of-h.patch > > [Test Case] > > * Configure a s390x system (z/VM guest or LPAR) with only a bit RAM, but lot's of DASDs devices. > > * Now gradually enable more and more DASDs and monitor the memory usage (be sure to exclude shared memory and cache). > > * One can notice a difference in mem usage of about 10:1 per activated DASD comparing the current stock 4.15 kernel with a patches kernel 4.15. > > * With about less than 1GB memory and 40+ DASD devices one may start to run into an OOM situation w(o the patch. > > [Regression Potential] > > * The regression potential can be considered as moderate, since: > > * this is purely s390x specific > > * it again only affects DASD disk storage (no zFCP/SCSI disk storage) > > * and it's again only limited to smaller systems (so more z/VM guests rather than LPARs). > > [Other Info] > > * A cherry-pick to 4.15 wasn't clean (problem in one line), hence the backport, which applied, compiled and worked fine. > > Stefan Haberland (1): > s390/dasd: reduce the default queue depth and nr of hardware queues > > drivers/s390/block/dasd.c | 13 +++++++++++-- > drivers/s390/block/dasd_int.h | 8 -------- > 2 files changed, 11 insertions(+), 10 deletions(-) > > -- > 2.7.4 > > > -- > kernel-team mailing list > kernel-team@lists.ubuntu.com > https://lists.ubuntu.com/mailman/listinfo/kernel-team