Dave Rigby daverigby

## GDB pretty printing of C++ STL.md

      
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                daverigby
                / GDB pretty printing of C++ STL.md
            
            
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              January 17, 2024 13:13
            
          
Install package libstdc++6 (Ubuntu 16.04)
Add following to ~/.gdbinit

python
import sys 
sys.path.insert(0, '/usr/share/gcc-9/python')
from libstdcxx.v6.printers import register_libstdcxx_printers
register_libstdcxx_printers (None)
end


## timestamp_delta.py
#!/usr/bin/env python3

"""Reads from stdin / arguments a sequence of lines which contain an
ISO 8601 timestamp, and outputs to stdout each line with the timestamp
with the delta from the previous line.

In other words, converts a file with absolute timstamps into a file
with relative timestamps since the previous line.

The first line cannot have a delta calculated, so it is reported as

## Grafana Tips.md

      
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                daverigby
                / Grafana Tips.md
            
            
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              June 27, 2023 17:05
            
          
Expressions on different stats - doesn't work due to extra name label which we need to discard:

sum without (name) (kv_ep_db_data_size_bytes{bucket="$bucket"}) / sum without (name) (kv_ep_db_file_size_bytes{bucket="$bucket"})

Heatmaps

Note: Set chart type to 'Heatmap' (top right), Series format to 'Heatmap'

Heatmap of KV opcode latencies:

sum by(le) (rate(kv_cmd_duration_seconds_bucket{opcode="ADD", bucket="$bucket"}[5m]))


## fix_date.py
#!/usr/bin/python
# fix_date.py - corrects the received date in IMAP folders.

# Description:
#     When moving mail between IMAP servers, the received date can become
#     reset to the date when the message was added to the new server. This
#     script attempts to fix this by setting the received date to the date the
#     message was sent.

# Usage:

## lvmcache_page_allocation_failure.md

      
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                daverigby
                / lvmcache_page_allocation_failure.md
            
            
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              March 22, 2023 11:52
            
          
    [Wed Mar 15 13:43:09 2023] AuxIoPool1: page allocation failure: order:0, mode:0x1000000(GFP_NOWAIT), nodemask=(null)
[Wed Mar 15 13:43:09 2023] AuxIoPool1 cpuset=/ mems_allowed=0
[Wed Mar 15 13:43:09 2023] CPU: 6 PID: 2760 Comm: AuxIoPool1 Not tainted 4.14.305-227.531.amzn2.aarch64 #1
[Wed Mar 15 13:43:09 2023] Hardware name: Amazon EC2 c6gd.2xlarge/, BIOS 1.0 11/1/2018
[Wed Mar 15 13:43:09 2023] Call trace:
[Wed Mar 15 13:43:09 2023]  dump_backtrace+0x0/0x190
[Wed Mar 15 13:43:09 2023]  show_stack+0x24/0x30
[Wed Mar 15 13:43:09 2023]  dump_stack+0x98/0xc8
[Wed Mar 15 13:43:09 2023]  warn_alloc+0x11c/0x1b4


## Profiling memcached.md

      
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                daverigby
                / Profiling memcached.md
            
            
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              March 2, 2023 11:48
            
          
    Step 1 - Gather profile


Install debuginfo package (in addition to main RPM/deb)
Install linux perf tools:

RHEL / CentOS / Amazon Linux: yum install perf.
Note: CentOS7 has a pretty old version of perf; which includes some issues decoding backtraces via DWARF. Prefer a newer version if possible. I have a local build of 5.11 for CentOS7 at ~/Documents/linux-perf-5.11-with-separate_debuginfo_unwind_fix


Start workload to be measured
Record profile

x86-64:


## socket_buffer_sizes
#include <errno.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>

void die(const char *f)
{
  printf("%s: %s\n", f, strerror(errno));

## V8 macOS load commands difference 8.3 vs 10.7.21.md

      
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                daverigby
                / V8 macOS load commands difference 8.3 vs 10.7.21.md
            
            
              Created
              September 30, 2022 18:56
            
          
    --- /Users/dave/Documents/MBs/MB-53924-v8_dyld/v8-8.3-cb5/libv8.dylib.load-commands	2022-09-30 19:52:49.000000000 +0100
+++ /Users/dave/Documents/MBs/MB-53924-v8_dyld/v8-10.7.21/libv8.dylib.load-commands	2022-09-30 19:53:03.000000000 +0100
@@ -1,23 +1,23 @@
-/Users/dave/Documents/MBs/MB-53924-v8_dyld/v8-8.3-cb5/libv8.dylib:
+/Users/dave/Documents/MBs/MB-53924-v8_dyld/v8-10.7.21/libv8.dylib:
 Load command 0
       cmd LC_SEGMENT_64
-  cmdsize 632
+  cmdsize 712


## cb_build_times_macos.md

      
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              February 11, 2022 13:33
            
              
                CB build times on macOS
              
          
    Results

TL;DR: Apple M1 Pro is ~3x faster to build compared to i9-8950HK (Coffee Lake).
MacBook Pro 2018

MacBook Pro (15-inch, 2018)

Processor: 2.9 GHz 6-Core Intel Core i9-8950HK CPU
Memory: 16 GB 2400 MHz DDR4
155.7s

  
## ns_server REST commands.md

      
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                daverigby
                / ns_server REST commands.md
            
            
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              December 9, 2021 16:07
            
              
                Useful ns_server REST commands
              
          
Change num_writer_threads from command-line

curl --user Administrator:asdasd -X POST --data "num_writer_threads=disk_io_optimized" http://localhost:9000/pools/default/settings/memcached/global

(Can also use num_reader_threads, and specify an exact number)

Change number of shards from command-line:

curl -i -u Administrator:asdasd --data 'ns_bucket:update_bucket_props("default", [{extra_config_string, "max_num_shards=64"}]).' http://localhost:9000/diag/eval
	#!/usr/bin/env python3

	"""Reads from stdin / arguments a sequence of lines which contain an
	ISO 8601 timestamp, and outputs to stdout each line with the timestamp
	with the delta from the previous line.

	In other words, converts a file with absolute timstamps into a file
	with relative timestamps since the previous line.

	The first line cannot have a delta calculated, so it is reported as
	#!/usr/bin/python
	# fix_date.py - corrects the received date in IMAP folders.

	# Description:
	# When moving mail between IMAP servers, the received date can become
	# reset to the date when the message was added to the new server. This
	# script attempts to fix this by setting the received date to the date the
	# message was sent.

	# Usage:
	#include <errno.h>
	#include <netinet/in.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/socket.h>

	void die(const char *f)
	{
	printf("%s: %s\n", f, strerror(errno));