On Wed, 2021-10-27 at 10:12 -0700, Yang Shi wrote:
> On Wed, Oct 27, 2021 at 5:48 AM Joakim Tjernlund
> <Joakim.Tjernlund@xxxxxxxxxxxx> wrote:
> >
> > Using a fairly minimal kernel I get a big difference in Reserved memory, using:
> > qemu-system-aarch64 -machine virt -kernel arch/arm64/boot/Image -cpu cortex-a53 -nographic -m 32M
> >
> > I get this:
> > Linux version 5.11.0
> > Memory: 24052K/32768K available (3520K kernel code, 684K rwdata, 548K rodata, 320K init, 245K bss, 8716K reserved, 0K cma-reserved)
> >
> > Versus:
> >
> > Linux version 5.10.75
> > Memory: 11836K/32768K available (3518K kernel code, 684K rwdata, 540K rodata, 320K init, 244K bss, 20932K reserved, 0K cma-reserved)
> >
> > Reserving 20 MB RAM on a 32 MB is way too much, even 8Mb is a bit much for us.
>
> This might be caused by the new lockless printk buffer patch
> introduced in 5.10. We noticed this spike on 5.10 kernel too. It may
> have much more memory reserved for meta data and the total amount may
> be as much as 3x of log_buf_len. The amount varies on different
> platforms with different configs. I didn't dig too much into the
> details to figure out how it gets the number.
>
> You could try to adjust CONFIG_LOG_BUF_SHIFT or set log_buf_len from
> kernel commandline to limit the printk buffer size.
I did try this by changing LOG_BUF_SHIFT but the resulting change was just minor.
To get some info about meminfo/zoneinfo I booted with an inird FS and got this:
Memory: 9576K/32768K available (3518K kernel code, 460K rwdata, 540K rodata, 320K init, 180K bss, 23192K reserved, 0K cma-reserved)
The initrd only added some 3 MB's
Here are meminfo/zoneinfo, not sure if they are useful though.
cat /proc/meminfo
MemTotal: 12416 kB
MemFree: 4644 kB
MemAvailable: 4064 kB
Buffers: 0 kB
Cached: 4788 kB
SwapCached: 0 kB
Active: 2500 kB
Inactive: 2524 kB
Active(anon): 2500 kB
Inactive(anon): 2524 kB
Active(file): 0 kB
Inactive(file): 0 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 248 kB
Mapped: 1844 kB
Shmem: 4788 kB
KReclaimable: 0 kB
Slab: 1712 kB
SReclaimable: 0 kB
SUnreclaim: 1712 kB
KernelStack: 384 kB
PageTables: 80 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 6208 kB
Committed_AS: 5636 kB
VmallocTotal: 262930368 kB
VmallocUsed: 324 kB
VmallocChunk: 0 kB
Percpu: 76 kB
HardwareCorrupted: 0 kB
cat /proc/zoneinfo
Node 0, zone Normal
per-node stats
nr_inactive_anon 631
nr_active_anon 625
nr_inactive_file 0
nr_active_file 0
nr_unevictable 0
nr_slab_reclaimable 0
nr_slab_unreclaimable 429
nr_isolated_anon 0
nr_isolated_file 0
workingset_nodes 0
workingset_refault_anon 0
workingset_refault_file 0
workingset_activate_anon 0
workingset_activate_file 0
workingset_restore_anon 0
workingset_restore_file 0
workingset_nodereclaim 0
nr_anon_pages 62
nr_mapped 461
nr_file_pages 1197
nr_dirty 0
nr_writeback 0
nr_writeback_temp 0
nr_shmem 1197
nr_shmem_hugepages 0
nr_shmem_pmdmapped 0
nr_file_hugepages 0
nr_file_pmdmapped 0
nr_anon_transparent_hugepages 0
nr_vmscan_write 0
nr_vmscan_immediate_reclaim 0
nr_dirtied 0
nr_written 0
nr_kernel_misc_reclaimable 0
nr_foll_pin_acquired 0
nr_foll_pin_released 0
nr_kernel_stack 384
pages free 1162
min 97
low 121
high 145
spanned 8192
present 8192
managed 3104
protection: (0, 0)
nr_free_pages 1162
nr_zone_inactive_anon 631
nr_zone_active_anon 625
nr_zone_inactive_file 0
nr_zone_active_file 0
nr_zone_unevictable 0
nr_zone_write_pending 0
nr_mlock 0
nr_page_table_pages 19
nr_bounce 0
nr_free_cma 0
pagesets
cpu: 0
count: 0
high: 0
batch: 1
vm stats threshold: 2
node_unreclaimable: 0
start_pfn: 262144
Node 0, zone Movable
pages free 0
min 0
low 0
high 0
spanned 0
present 0
managed 0
protection: (0, 0)
