| Upstream-Status: Backport |
| Signed-off-by: Ross Burton <ross.burton@arm.com> |
| |
| PR28804: tune default stap -s ## buffer size on small RAM machines |
| |
| Insert a forgotten division by num_online_cpu() to adjust downward the |
| calculated bufsize. Tweak normal defaults back to 128 * 2 * 64K |
| (16MB) per CPU, as the stap man page indicates. This may need further |
| tweaking when balancing against staprun consumption performance, but |
| at least we have the docs lined up with the code at the moment. |
| |
| PR28804: tune default stap -s ## buffer size on small RAM machines |
| |
| Use si_meminfo to limit default buffer size. Note in the man page |
| that the "-s ##" parameter is per-CPU. |
| |
| diff --git a/man/stap.1.in b/man/stap.1.in |
| index 55dbc2c93..285a27b34 100644 |
| --- a/man/stap.1.in |
| +++ b/man/stap.1.in |
| @@ -239,8 +239,8 @@ and average amount of time spent in each probe-point. Also shows |
| the derivation for each probe-point. |
| .TP |
| .BI \-s " NUM" |
| -Use NUM megabyte buffers for kernel-to-user data transfer. On a |
| -multiprocessor in bulk mode, this is a per-processor amount. |
| +Use NUM megabyte buffers for kernel-to-user data transfer per processor. |
| +The default is 16MB, or less on smaller memory machines. |
| .TP |
| .BI \-I " DIR" |
| Add the given directory to the tapset search directory. See the |
| diff --git a/runtime/transport/transport.c b/runtime/transport/transport.c |
| index 18ecccea2..44afff814 100644 |
| --- a/runtime/transport/transport.c |
| +++ b/runtime/transport/transport.c |
| @@ -72,8 +72,11 @@ static inline void _stp_unlock_inode(struct inode *inode); |
| #include "procfs.c" |
| #include "control.c" |
| |
| -static unsigned _stp_nsubbufs = 256; |
| -static unsigned _stp_subbuf_size = 8 * STP_BUFFER_SIZE; /* 64K */ |
| +/* set default buffer parameters. User may override these via stap -s #, and |
| + the runtime may auto-shrink it on low memory machines too. */ |
| +/* NB: Note default in man/stap.1.in */ |
| +static unsigned _stp_nsubbufs = 128; |
| +static unsigned _stp_subbuf_size = 2 * STP_BUFFER_SIZE; /* 2 * 64K */ |
| |
| /* module parameters */ |
| static int _stp_bufsize; |
| @@ -602,17 +605,30 @@ static int _stp_transport_init(void) |
| _stp_need_kallsyms_stext = 0; |
| #endif |
| |
| - if (_stp_bufsize) { |
| - unsigned size = _stp_bufsize * 1024 * 1024; |
| + if (_stp_bufsize == 0) { // option not specified? |
| + struct sysinfo si; |
| + long _stp_bufsize_avail; |
| + si_meminfo(&si); |
| + _stp_bufsize_avail = (long)((si.freeram + si.bufferram) / 4 / num_online_cpus()) |
| + << PAGE_SHIFT; // limit to quarter of free ram total |
| + if ((_stp_nsubbufs * _stp_subbuf_size * num_online_cpus()) > _stp_bufsize_avail) { |
| + _stp_bufsize = max_t (int, 1, _stp_bufsize_avail / 1024 / 1024); |
| + dbug_trans(1, "Shrinking default _stp_bufsize to %d MB/cpu due to low free memory\n", _stp_bufsize); |
| + } |
| + } |
| + |
| + if (_stp_bufsize) { // overridden by user or by si_meminfo heuristic? |
| + long size = _stp_bufsize * 1024 * 1024; |
| _stp_subbuf_size = 65536; |
| + // bump up subbuf size from 64K to 1M to keep _stp_nsubbufs not too large |
| while (size / _stp_subbuf_size > 64 && |
| _stp_subbuf_size < 1024 * 1024) { |
| _stp_subbuf_size <<= 1; |
| } |
| _stp_nsubbufs = size / _stp_subbuf_size; |
| - dbug_trans(1, "Using %d subbufs of size %d\n", _stp_nsubbufs, _stp_subbuf_size); |
| } |
| - |
| + dbug_trans(1, "Using %d subbufs of size %d\n", _stp_nsubbufs, _stp_subbuf_size); |
| + |
| ret = _stp_transport_fs_init(THIS_MODULE->name); |
| if (ret) |
| goto err0; |