feat: control perf with fifo

benchmarks/perf.nim

@@ -0,0 +1,49 @@
+# Simple utils for controlling perf tracing through fifos.
+# After creating ack and control fifos with mkfifo, you can use this with:
+#
+# perf record -g \
+#     --delay -1 \
+#     --control fifo:./perf-ctl,./perf-ack \
+#     --call-graph dwarf \
+#     -F 99 \
+#     -o perf.data -- [command]
+
+import std/strformat
+import std/strutils
+
+import pkg/questionable/results
+
+type Perf* = object
+  ctl_file: File
+  ack_file: File
+
+proc attach*(Perf: type, ctl_fifo: string, ack_fifo: string): ?!Perf =
+  var perf: Perf
+  if not open(perf.ctl_file, ctl_fifo, fmWrite):
+    return failure("Failed to open ctl fifo")
+  if not open(perf.ack_file, ack_fifo, fmRead):
+    return failure("Failed to open ack fifo")
+
+  success(perf)
+
+proc detach*(self: Perf) =
+  self.ctl_file.close()
+  self.ack_file.close()
+
+proc send*(self: Perf, cmd: string): ?!void =
+  self.ctl_file.write(cmd)
+  self.ctl_file.flushFile()
+
+  let response = self.ack_file.readLine()
+  # Ideally equality should work, but in practice we get some garbage
+  # characters sometimes.
+  if not ("ack" in response):
+    return failure(&"Error {response} received from perf")
+
+  success()
+
+proc perfOn*(self: Perf): ?!void =
+  send(self, "enable")
+
+proc perfOff*(self: Perf): ?!void =
+  send(self, "disable")

benchmarks/repostore_rw_bench.nim

@@ -11,23 +11,7 @@ import pkg/codex/merkletree/codex
 import pkg/codex/manifest
 import pkg/codex/stores/[filestore, repostore]
 
-let
-  PR_TASK_PERF_EVENTS_DISABLE {.
-    importc: "PR_TASK_PERF_EVENTS_DISABLE", header: "<linux/prctl.h>"
-  .}: cint
-  PR_TASK_PERF_EVENTS_ENABLE {.
-    importc: "PR_TASK_PERF_EVENTS_ENABLE", header: "<linux/prctl.h>"
-  .}: cint
-
-proc prctl(
-  option: cint, args: varargs[culong]
-): cint {.importc: "prctl", header: "<sys/prctl.h>".}
-
-proc perfOn() =
-  assert prctl(PR_TASK_PERF_EVENTS_ENABLE) == 0
-
-proc perfOff() =
-  assert prctl(PR_TASK_PERF_EVENTS_DISABLE) == 0
+import ./perf
 
 const
   NBlocks = 163_840
@@ -118,6 +102,12 @@ proc readData(
 proc runRepostoreBench(
     dataset: Dataset
 ): Future[void] {.async: (raises: [CatchableError]).} =
+  let perf = Perf.attach("./perf-ctl", "./perf-ack").expect(
+      "failed to locate perf ctl/ack files"
+    )
+
+  perf.perfOff().expect("failed to disable perf")
+
   let
     dir = createTempDir("repostore-bench", "")
     store = newRepostore(dir)
@@ -129,13 +119,19 @@ proc runRepostoreBench(
   benchmark "repostore write data":
     await writeData(dataset, store)
 
+  perf.perfOn().expect("failed to enable perf")
+
   benchmark "repostore read data":
     await writeData(dataset, store)
 
 proc runFilestoreBench(
     dataset: Dataset
 ): Future[void] {.async: (raises: [CatchableError]).} =
-  perfOff()
+  let perf = Perf.attach("./perf-ctl", "./perf-ack").expect(
+      "failed to locate perf ctl/ack files"
+    )
+
+  perf.perfOff().expect("failed to disable perf")
 
   let
     dir = createTempDir("filestore-bench", "")
@@ -148,11 +144,11 @@ proc runFilestoreBench(
   benchmark "filestore write data":
     await writeData(dataset, store)
 
-  perfOn()
+  perf.perfOn().expect("failed to enable perf")
 
   benchmark "filestore read data":
     await readData(dataset, store)
 
 let dataset = makeDataset(NBlocks, BlockSize).tryGet()
-# waitFor runRepostoreBench(dataset)
-waitFor runFilestoreBench(dataset)
+waitFor runRepostoreBench(dataset)
+#waitFor runFilestoreBench(dataset)