On 19.02.2018 17:33, David Sterba wrote: > On Thu, Feb 15, 2018 at 10:59:47PM -0500, je...@suse.com wrote: >> From: Jeff Mahoney <je...@suse.com> >> >> The srcu_struct in btrfs_fs_infoa scales in size with NR_CPUS. On >> kernels built with NR_CPUS=8192, this can result in kmalloc failures >> that prevent mounting. >> >> There is work in progress to try to resolve this for every user of >> srcu_struct but using kvzalloc will work around the failures until >> that is complete. > > Interesting, the subvol_srcu is the worst contirbutor of the fs_info > size, on a config with NR_CPUS=512: > > struct srcu_struct subvol_srcu; /* 1064 3480 */ > ... > /* size: 6496, cachelines: 102, members: 181 */ > > Using kvzalloc makes sense and is a minimal fix. In the longterm I'd > rather allocate subvol_rcu dynamically so the whole fs_info is not > vmalloced (in the rare case when kmalloc would not work). As this is > unpredictable and almost invisible, I'm worried about some random > effects (performance, virtual mappings), so it would be better to avoid > them if possible.
The interesting bit is the "there is WIP trying to address this". Are there any patches that have been sent to lkml? > > Reviewed-by: David Sterba <dste...@suse.com> > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
