From 33435e288deb7903d770578267b793f56ad6c46b Mon Sep 17 00:00:00 2001
From: Alex Saveau <saveau.alexandre@gmail.com>
Date: Tue, 30 Jul 2024 23:22:12 -0700
Subject: [PATCH] Rework pipelining to avoid kernel buffering

Signed-off-by: Alex Saveau <saveau.alexandre@gmail.com>
---
 cli/src/main.rs | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/cli/src/main.rs b/cli/src/main.rs
index 1059514..8206eaf 100644
--- a/cli/src/main.rs
+++ b/cli/src/main.rs
@@ -813,7 +813,7 @@ fn garbage_collect(
             }
         }
 
-        drain_requests(recv, true, &mut pending_requests)?;
+        drain_requests(recv, 0, &mut pending_requests)?;
         println!("Removed {num_duplicates} duplicate entries.");
     }
 
@@ -900,12 +900,7 @@ fn migrate_from_gch(
                 let gch_id = gch_id!();
                 if translation.len() <= gch_id {
                     unsafe {
-                        drain_add_requests(
-                            &server,
-                            true,
-                            Some(&mut translation),
-                            &mut pending_adds,
-                        )?;
+                        drain_add_requests(&server, Some(&mut translation), &mut pending_adds)?;
                     }
                 }
                 translation[gch_id]
@@ -984,7 +979,7 @@ fn migrate_from_gch(
         }
     }
 
-    unsafe { drain_add_requests(server, true, None, &mut pending_adds) }
+    unsafe { drain_add_requests(server, None, &mut pending_adds) }
 }
 
 fn migrate_from_clipboard_indicator(
@@ -1087,7 +1082,7 @@ fn migrate_from_clipboard_indicator(
         }
     }
 
-    unsafe { drain_add_requests(server, true, None, &mut pending_adds) }
+    unsafe { drain_add_requests(server, None, &mut pending_adds) }
 }
 
 fn migrate_from_gpaste(
@@ -1236,7 +1231,7 @@ fn migrate_from_gpaste(
         }
     }
 
-    unsafe { drain_add_requests(server, true, None, &mut pending_adds) }
+    unsafe { drain_add_requests(server, None, &mut pending_adds) }
 }
 
 #[allow(clippy::cast_precision_loss)]
@@ -1568,7 +1563,7 @@ fn migrate_from_ringboard_export(
         }
     };
 
-    unsafe { drain_add_requests(server, true, None, &mut pending_adds) }
+    unsafe { drain_add_requests(server, None, &mut pending_adds) }
 }
 
 fn generate(
@@ -1610,7 +1605,7 @@ fn generate(
         }
     }
 
-    unsafe { drain_add_requests(server, true, None, &mut pending_adds) }
+    unsafe { drain_add_requests(server, None, &mut pending_adds) }
 }
 
 fn fuzz(
@@ -1887,7 +1882,7 @@ fn fuzz(
                                 verbose,
                             )
                         },
-                        true,
+                        0,
                         &mut pending_requests[idx],
                     )?;
 
@@ -2022,7 +2017,7 @@ fn fuzz(
                                 verbose,
                             )
                         },
-                        true,
+                        0,
                         pending_requests,
                     )?;
                     debug_assert!(pending_ops.is_empty());
@@ -2047,7 +2042,10 @@ fn pipeline_request(
     mut recv: impl FnMut(RecvFlags) -> Result<(), ClientError>,
     pending_requests: &mut u32,
 ) -> Result<(), CliError> {
-    let mut retry = false;
+    if *pending_requests >= 8 {
+        drain_requests(&mut recv, *pending_requests / 2, pending_requests)?;
+    }
+
     loop {
         match send(if *pending_requests == 0 {
             SendFlags::empty()
@@ -2058,8 +2056,7 @@ fn pipeline_request(
                 if e.kind() == ErrorKind::WouldBlock =>
             {
                 debug_assert!(*pending_requests > 0);
-                drain_requests(&mut recv, retry, pending_requests)?;
-                retry = true;
+                drain_requests(&mut recv, *pending_requests / 2, pending_requests)?;
             }
             r => {
                 r?;
@@ -2073,11 +2070,11 @@ fn pipeline_request(
 
 fn drain_requests(
     mut recv: impl FnMut(RecvFlags) -> Result<(), ClientError>,
-    all: bool,
+    remaining: u32,
     pending_requests: &mut u32,
 ) -> Result<(), CliError> {
     while *pending_requests > 0 {
-        match recv(if all {
+        match recv(if *pending_requests > remaining {
             RecvFlags::empty()
         } else {
             RecvFlags::DONTWAIT
@@ -2085,7 +2082,7 @@ fn drain_requests(
             Err(ClientError::Core(CoreError::Io { error: e, .. }))
                 if e.kind() == ErrorKind::WouldBlock =>
             {
-                debug_assert!(!all);
+                debug_assert!(*pending_requests <= remaining);
                 break;
             }
             r => r?,
@@ -2131,11 +2128,10 @@ unsafe fn pipeline_add_request(
 
 unsafe fn drain_add_requests(
     server: impl AsFd,
-    all: bool,
     translation: Option<&mut Vec<u64>>,
     pending_adds: &mut u32,
 ) -> Result<(), CliError> {
-    drain_requests(pipelined_add_recv(server, translation), all, pending_adds)
+    drain_requests(pipelined_add_recv(server, translation), 0, pending_adds)
 }
 
 fn generate_random_entry_file(